The Reverse Diet

Define

The Problem: Metabolic Damage

What is a Reverse Diet?

Reverse dieting is a specific dietary theory that involves gradually increasing your caloric energy over several weeks or months allowing your metabolism to adjust upward and return to normal after a prolonged period of very low calorie intake thus preventing fat regain (often referred to as yo-yoing).

This increase in caloric intake after a prolonged low calorie diet is referred to as a “Reverse Diet” or "metabolism reset". It has become a go-to solution for a new coach when a client explains they are barely eating anything and can’t understand why they aren’t losing weight. It has been elevated to a catch-all magical solution to a problem that hasn't been adequately defined, measured or analyzed yet. The science behind Reverse Dieting as a solution to metabolic damage is known and quantified in numerous studies, but most health coaches over-diagnose the condition without adequate testing and significantly overestimate its impact. It is more than likely not the answer to the weight loss dilemma you were hoping for.

As a Physiologist I have been studying and working with metabolism issues for 2 decades. I have performed over 1000 medical grade metabolic tests on many populations including those with eating disorders. I see the same issue raised regularly from health coaches regarding the individual who is eating a low calorie diet and not losing weight. More often than not, it is a body composition and or BMI classified overweight or obese individual needing to lose 10% of their bodyweight or often much more.

The first inclination of the coach is to assume metabolic damage caused by extreme prolonged low caloric intake. The solution they immediately move to is to increase the caloric intake of the client (Reverse Diet) without performing any advanced testing, probing of how the client is tracking intake or exploring the emotional burdens that some individuals carry with them in their never-ending weight loss journey.

Accepting the Client’s input is one step in the first stage of a health practice. Verification through observation, testing, and analyzation are the keys to establishing a professional approach to a sophisticated and complex health problem. This initial stage is what we refer to as Defining the problem subjectively in the eyes of the client and objectively in the eyes of the health practitioner. It is part of our DMAIC approach to a health practice (Define - Measure - Analyze -Improve - Control).

Our second stage is to measure the extent of the problem if it is identified as an issue, using the data collected in the measurement phase to weigh its significancy to a potential solution.

In the case of metabolic damage, during the measurement and analyze stages, you will find that Reverse Dieting as a solution doesn’t contribute as heavily to the weight loss answer as most have been led to believe.

The Answer: Reverse Dieting Works But...

Let me cut to the chase in case you are not inclined to read the research or consume the educational content contained in this article. Metabolic damage exists. It's just not as severe as you have somehow been led to believe, it doesn't happen in all cases and it is readily resolved by having your client eat normally for anywhere from a few days to a few weeks before metabolism is restored to normal.

That being said, your client is more than likely not reporting caloric intake properly for reasons you need to discover. That's the hard part. When you perform the metabolic math I will show you below, the potential metabolic damage from a low calorie diet will not likely explain why the caloric deficit the client says they are creating is not resulting in weight loss.

Like I said, metabolic damage is real, supported and quantified in the scientific literature and can be readily solved with a short period of normalized caloric intake but it is the extent of the damage that is confusing Coaches and Clients. If you want to know more about the range of the metabolic damage, how to determine if metabolic damage exists or how to rule it out, what a Reverse Diet accomplishes and when to use it, then read on...  but fair warning, I will demonstrate why the scientific literature support for metabolic damage and reverse dieting is not likely to solve the reason your client is not losing weight.

Measure

Metabolic Chemistry

We follow a scientific approach towards human chemistry and physiology meaning our method to weight loss is agnostic and the only thing that is important is the energy formulas. There are many variables that can affect the formula up or down but the equation is still the universal truth when it comes to weight. What we do support is that the human chemistry and how it manifests itself in symptomatic ways will give you clues as to how to determine the source of a health problem and with a proper framework and approach, the best ways to change it.

It doesn't matter if the issue is related to hormones, variations of macronutrient profiles, or improper tracking, the reasons are always scientifically accounted for within the energy formulas.

Additionally, if you break this science down to its atomic parts accounting for carbon, hydrogen and oxygen atoms you can further explain how the energy formulas work, why you weigh what you weigh and the related affects to human hormonal chemistry as it relates to the changes in the energy formula.  

Atoms such as oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus are the most abundant and together account for more than 98% of body weight. These atoms are the basic components that make up all the molecules in the body such as water, lipids, proteins, minerals, and carbohydrates. Molecules are the building blocks of the body's tissue such as Muscle, Adipose tissue, Blood, Bone, Skin, Liver or what is commonly referred to as fat, muscle, bones, organs and fluids.

Atoms build molecules and molecules make tissue and fluids. Reverse dieting doesn't change this universal fact, it only acts on the variables that increase or decrease efficiency of the process. Essentially, how you eat, move, rest and live can make your VO2 (volume of oxygen consumption) more or less efficient.  As such, the metabolic damage a coach may seek to fix with a reverse diet affects VO2 and can be measured precisely (Indirect calorimetry) as it has in many scientific studies, but it is not likely the main reason or maybe not even any part of the reason an individual isn't losing weight.

So you are made of atoms and you don't create atoms from nothing, they have to be ingested, breathed in or injected into your body to cause increases in weight. They need to be breathed out, sweated out, urinated out or defecated out to lose weight.

There are two caveats to weight gain or loss that need to be considered in evaluating weight fluctuations. The first is digestion. Not all energy is digested and metabolic chemistry requires digestion into the blood stream to be impactful into the energy equation. The second is water. The water molecule, H2O, makes up as much as 70% of your bodyweight and can fluctuate significantly and is often the chemical reason weight fluctuates rapidly from day to day or week to week.

Body composition at the atomic level of a 70 kg reference man:

Introduction to Human Nutrition
Second Edition
Wiley-Blackwell
A John Wiley & Sons, Ltd., Publication
© 2009, 2002 by The Nutrition Society

Lungs are the primary excretory organ for fat. In order to burn fat, you must unlock the carbon stored in fat cells so it can be breathed back out of the body as CO2. “Eat less and move more” starts to make more sense when you understand the chemistry of weight loss.  Knowledge of VO2 and the chemistry of metabolism is an advanced art but it explains what many health professionals are reluctant to accept; you just don't make fat from thin air, it takes molecules to gain weight and you get those molecules through caloric intake. The only way to lose weight is to eliminate those molecules. The physics and human biological chemistry is beyond the scope of this article but isn’t necessary to understand in order to accept the scientific literature on Caloric theory explored here. That being said if you wish to learn more about this topic watch this extraordinary Ted Talk on the subject by a top physicist. 

"If you exclude the possibility of atoms magically appearing inside your body, as the laws of physics say you should, then there are only two ways a human being can become overweight: 1) eating too many atoms, or 2) not exhaling enough of them." 

- Ruben Meermen Physicist

This is another piece of learning content I am going to reserve for a future lesson but suffice to say molecules and fluids have a specific weight and that weight as it enters and leaves the body through normal mechanisms accounts for weight gain and weight loss. “Calories” is merely a way to express the thermal heat energy of how those molecules change, are used and eliminated from the body. It is a proverbial measuring stick.

Verifying Metabolic Damage

The DMAIC Framework further divides into 4 subcategorizes the various methodologies that can be used for Defining, Measuring and Analyzing data:

Screen, Assess, Test and Survey, to be used in the order in which the method makes the most sense for meeting the goals of each phase of the DMAIC framework. The methods are agnostic as long as they meet the needs of the health practitioner and follow best scientific practices. 

Screen: Observation

Your first series of tests when a client tells you they have been eating a very low calorie diet for a prolonged period and not losing weight is visual. A person eating less than their RMR for an extended period of time is not only thin but likely will look malnourished with a visible loss of muscle tissue. The one exception is if they were previously obese and had been losing weight which is addressed in the next step. That being said, if they were eating at or below RMR they would still be on a weight loss trajectory albeit at a slower pace unless their RMR intake was calculated when they were significantly heavier.

Assess: Body Composition, BMI

Second, you want to determine if they are classified as overweight or obese. Calculate their BMI and if you are able to, measure their body composition. If they are categorized as overweight or obese by percent body fat or even by BMI, it is likely they are not eating a low calorie diet and are at or above their Resting Metabolic Rate (RMR). At this point you can begin to rule out metabolic damage from under-eating. As you will see in the research, a very low calorie diet may slow weight loss when continuing to consume in an energy deficit, but you wouldn't gain weight unless you were eating too much. The one exception to this rule is if the client was much more obese previously and although having lost weight, was still classified as overweight due to a theoretical plateau.  At this point you need to perform a new energy calculation and apply the potential metabolic damage factors discussed in the Metabolic Math section within the Analyze framework phase below and determine if their self-reported energy intake is accurate.

Survey: Nutritional Intake Journal and Interview

If they are overweight then begin reviewing their daily nutritional journal for obvious errors or omissions. Interview them about their journal, their daily lifestyle and their eating habits.

Stress testing your assumptions and supporting with data will allow you to begin to drill down as to if the caloric intake is accurate. If it is accurate and they are thin or gaunt then you may likely have an eating disorder for which just increasing calories will not solve. 

Test: Direct and Indirect calorimetry

The next and more high level of testing is to perform a metabolic test to determine actual Resting Metabolic Rate with a medical grade metabolic cart using indirect calorimetry. This could also be performed with a $1500 24 hour stay in a metabolic chamber (direct calorimetry) but the $200-$300 metabolic cart takes only 20 minutes and is virtually as accurate.

Direct Calorimetry in a metabolic chamber

These structures are called whole-room calorimeters. Direct calorimetry provides a measure of energy expended in the form of heat. There are very few in the world and have not been traditionally available to the public as they are reserved for research. These are the Gold standard in metabolism measurements.

Another interesting article about the experience of being in a metabolic chamber and the related metabolic truths and myths can be found here:
What I learned about weight loss from spending a day inside a metabolic chamber

This test is invaluable for metabolic calculations and determining more precisely the level of a client's natural metabolism. The metabolic cart seen below, measures the molecular chemistry of what is being breathed in and expired from the body which has a direct correlation with energy consumption. It is how many energy equations are determined or tested in most research studies where a chamber in not available or cost prohibitive. It is also how they determine the energy needs of a comatose patient in the hospital. It also will rule out or quantify the extent if any metabolic damage. A metabolic cart is the Gold Standard #2 as it is extremely accurate, often used in academic research, but not quite as dynamic and encompassing as a chamber due to the 24 hour of monitoring but more readily available and affordable.

The one caveat which I cover below in the "Improve" section, is that, "if" the metabolic test determines that the Resting Metabolic Rate is below normal, without a baseline it may be hard to determine if the issue is metabolic damage or genetically low metabolism or possibly related to other reasons. Time and additional tests as the client becomes healthier and returns to normal eating habits will determine the answer.

Indirect calorimetry with a Metabolic Cart

Indirect calorimetry is the method by which metabolic rate is estimated from measurements of oxygen consumption and carbon dioxide production and is based on a series of assumptions and equations. Indirect calorimeters can measure energy expenditure in both mechanically ventilated and spontaneously breathing patients. The measurement is based on the assumption that all the O2 consumed (VO2) is used to oxidize degradable fuels and all the CO2 produced (VCO2) in the body is recovered. An extremely precise RMR can be ascertained using a metabolic cart and used to determine the extent if any of metabolic damage.

Hormone affects on metabolism

If any of the above tests support an unusually slow metabolism as compared to norms, it may be prudent to refer the client to a qualified practitioner for a hormonal profile. Most metabolic damage scenarios are attributed to hypothyroidism (a low level of Thyroid production). Small decreases in thyroid hormone can affect metabolism and is a health issue but as it applies to weight gain, it should be noted that the American Thyroid Association has stated:

"The cause of the weight gain in hypothyroid individuals is also complex, and may not be related to excess fat accumulation. Most of the extra weight gained in hypothyroid individuals is due to excess accumulation of salt and water. Massive weight gain is rarely associated with hypothyroidism. In general, 5-10 pounds of body weight may be attributable to the thyroid, depending on the severity of the hypothyroidism."  

Further they state "Since much of the weight gain in hypothyroidism is accumulation in salt and water, when the hypothyroidism is treated one can expect a small (usually less than 10% of body weight) weight loss."

American Thyroid Association

There are many other chemical factors that can affect things like Leptin which is a hormone your adipose tissue (body fat) releases that helps your body maintain your normal weight on a long-term basis. It does this by regulating hunger by providing the sensation of satiety (feeling full). Very low calorie diets as well as other hormone disruptors can reduce Leptin or create what is known as Leptin resistance thus causing people to want to eat more and reduce self restraint. Although not directly related to slowing metabolism it does affect energy intake. Further studies are still needed to understand if there is any direct affect on metabolism.   

Analyze

Metabolic Math

Through all my post graduate studies, research and 20 years of clinical experience, I have never seen or read about a person in the scientific literature who was 200 or 220 pounds and clearly overweight, that didn’t lose weight on a 1200-1400 calorie diet. It defies physics and no metabolism has ever been recorded to down regulate that much except in rare disorders for which the patient was not healthy and usually underweight. Individuals that don’t eat enough eventually emaciate and become thin and gaunt.

This is not mystery science, we do understand it and we can explain all aspects of it. What we don't understand as well is exactly the why and how much a micro part of the energy equation affects metabolism, but we can measure it in its totality and understand when something affects the total energy number. Tailoring the application and the exact numbers to billions of different people is the art. Unfortunately, precise energy formulas are extremely difficult to estimate accurately as it takes scientific equipment and assessment testing to get a good starting point. This equipment is readily available but maybe not within the reach of every health practitioner. The health and nutrition industry often uses population formulas instead, but unfortunately they just don't fit everyone perfectly. With the proper medical equipment we can get much more precise.

That being said, never accept the fact that although you may not be able to afford the high-end scientific equipment or have not studied the knowledge base to the level of a Masters or PhD as a valid reason that a scientific formula or theory must not be true or that you can't find a better answer to the problem. For most coaches it takes experimentation with each individual to hone in on the right method, you won't likely nail it the first time just using population formulas. It make take several iterations of analysis or surveys to discover the right range to work from.

Unfortunately, for a number of reasons starting with a lack of chemical-metabolic knowledge, stubbornness or close minded approach or maybe even laziness, health coaches become frustrated to the point that they seek alternative theories that have no basis in science. Resist the temptation. If you have made it this far in this article then congratulations on being in a small group of professional health practitioners wanting to follow the science and find real answers to health problems to optimize their Client's results.

Metabolic Damage Quantified

Most studies on low calorie or very low calorie diets, have shown metabolic damage or reductions in RMR in the range of 10% (see research below) which is normally about 125-200 calories depending on the size of the person. Realize RMR varies widely among the population and is affected by height, gender, body composition, age and various other external factors like nutrition, medicine, disease… We are assuming an individual is likely within 3 standard deviations of the median population curve on RMR which is a scientifically valid assumption. Given that, research has shown that even when testing the RMR population norm formulas such as the Harris-Benedict equation, against actual metabolism using indirect calorimetry with a metabolic cart, the differences are usually not significant enough to be the reason someone doesn’t lose weight when caloric intake is adequately below the population equations. We have generally observed indirect calorimetry to be higher more often than below the population formulas. In addition we have seen indirect calorimetry above the formulas by as much as 30% but rarely below the formulas more than 10-15%.

Resting Metabolic Rate (RMR)

RMR is often commonly exchanged with the term BMR (Basil Metabolic Rate). The differences are minor and for our purposes we will refer to RMR as that is most commonly used. It should be noted that in most cases we will be computing RMR using a population norm equation such as the Harris-Benedict formula, but it must be understood that these formulas are not perfect and much of the population may be genetically above or below these norms.

Resting metabolic rate is the total number of calories burned when your body is completely at rest to support basic life functions such as breathing, circulating blood, organ functions, and basic neurological functions. It accounts for virtually 100% of your energy requirements when at rest or sleeping but in general about 60-75% of your overall energy needs during a 24 hour period. When metabolic damage exists, it affects RMR and Reverse Dieting is the term the health market has coined for increasing caloric intake to normal levels to fix the metabolic damage. Knowing how to Reverse Diet when you don't have a diagnostic to determine metabolic damage is merely a guess.

You will see in the studies below that metabolic damage from prolonged low calorie intake rarely exceeds 10% of RMR which would be approximately 160 calories in the average sized man with an RMR of 1600 calories or 140 calories in the average sized woman with an RMR of 1400 calories. This metabolic damage doesn't explain the fact that an individual is not losing weight on a very low calorie diet as science dictates that the progress would slow but not halt. As RMR normally makes up as much as 60-75% of total daily expenditures, the total energy expenditures for the day could be as high as 2100-2700 calories. The average man with a damaged RMR of 1440 calories also expends energy for normal activities (non-exercise activity thermogenesis - NEAT) and exercise (thermic effect of physical activity - TEPA) during the course of the day as well as digestion (thermic effect of food - TEF) increasing his total caloric burn rate to levels above 2000 calories in this case even with metabolic damage. Even in rare instances that metabolic damage increases to levels of 20%, the total energy burned would still be high enough to continue weight loss during low levels of caloric intake. Weight loss merely slows but does not stop.

Further the National Academy of Sports Medicine (NASM) has published this data on their website:

NASM Position on Low Calorie Intake

“Thirty years of research demonstrates how the practice of eating very low caloric intakes (e.g., starvation, 800-calorie diets) can suppress RMR, a number that by some estimates can be as high as 20%. Under this stress, sustained, elevated levels of cortisol can suppress thyroid stimulating hormone production which will ultimately impact thyroid hormones that regulate metabolism. Furthermore, these starvation states can also waste away valuable muscle mass which in turn will also reduce RMR.”

So the debate isn’t if the affect of metabolic damage is real, but the extent of how it impacts weight loss in the presence of continued low caloric intake. If you were to return immediately to a maintenance level diet then you may gain weight given the lower energy expenditures from metabolic damage caused by the chronically low caloric diet. But returning to a higher calorie intake a.k.a. "Reverse Dieting", has been shown in the literature to return RMR to normal levels within days or a few weeks. If you maintain a low calorie diet you will continue losing weight, albeit at a slower pace than normal.

Improve

The Solution

I mention all of the above so coaches are not chasing ghosts and trying to solve an imaginary problem. The problem you need to solve may be much more difficult than prescribing a Reverse Diet. Although they could be tracking their intake wrong, the more likely problem is that their relationship with food and shame that being overweight creates for them causes them to deflect by outwardly projecting a lack of fault due to the fact they can’t control their chemistry.

There are many reasons to try some "reverse dieting" but first you need to determine during the Analyze stage above, if the minor drop in metabolism of what has been shown in most research to be 8-12% can account for the fact that the caloric deficit is not working. If it does not account for the lack of weight loss, you must begin to reanalyze how the client is tracking energy intake and the where and why errors may exist.

If the problem is indeed errors in measuring and tracking these are easily flushed out. If the omissions are deliberate or subconscious, the problem to be solved is much more complex. Getting them to understand that this isn’t about fault or blame and that there is no shame in facing reality is no small task before a health practitioner has built a level of trust and respect with their client. This is a higher level of consulting than just getting someone to eat a specific number of calories. It is the most complex of issues a nutrition coach can face and helping a client to get past it is without a doubt a talent and technical education that goes beyond what most trainers have in their arsenal. My hat is off with respect to those that can succeed with such clients, it’s truly a gift.

Reverse Diet Science

There is proof that there is some reduction in metabolism/RMR when on a low calorie or sustained reduced calorie diet that more often is suggested to be caused by a loss of metabolically active tissue or more commonly muscle tissue during weight loss. There are numerous studies also implicating a reduction in key chemicals due to low caloric diets such as T3 which may also suppress metabolism. But as you will see below this is not always proven to be true either.

There is not a lot of official scientific reference to "Reverse Dieting" per se, but rather a return to a normally healthy diet to fix any metabolic damage that has been incurred. In most cases the problem if any was remedied in a matter of a few days or a week or two. 

Reverse Dieting is click bait and suggesting it works or doesn't work in the title can never be trusted until you read the whole article. The definitions and the explanations of what the author or researcher are explaining to support a position can make almost everyone right in this debate. As such I like to stick to the physics, the math, the chemistry... and leave the emotional empathic application of the client’s why and how to others in the field closer to the client and maybe more skilled in human behavior change.

As I mentioned, when an individual is on a very low or extremely low calorie diet, even a variation in RMR or any kind of metabolic damage normally in the range of 10%, is not enough to account for a total lack of weight loss in most overweight individuals. That all being said we have performed thousands of tests with a medical grade metabolic cart using indirect calorimetry. We have personally experienced and the literature supports, as much as 30% swings in RMR from the norms in otherwise perfectly healthy individuals that are not dieting and are eating normally. The formula norms we use are really a tool for an average individual and a lot of the population will fall to the left or the right of the bell curve as is the nature of population equations.

You really don't even know if the suggested reduction in RMR/metabolism after a low caloric diet is truly metabolic damage resulting from a prolonged low calorie diet unless you tested the RMR baseline before the low-calorie diet began. As such they could be 10-30% below the norms before they even start changing their eating habits. The reasons are numerous, but you can see the approach to assume they aren't losing weight because of a sustained low-calorie diet is not evident on its face and requires much more exploration and testing before and after such diet. Pronouncing that the client has metabolic damage is irresponsible in the absence of adequate scientific testing.

To the extent that they had less than optimal metabolism before a Coach begins working with them, and or if they indeed have been experiencing depressed metabolism even of 10% due to sustained low caloric intake (see research below), then a theoretical reverse diet would help fix these issues but not to the extent it is often claimed and as such why there isn't specific support for reverse dieting in the scientific literature to this extent. For example, a 200 pound man that is overweight by 20-25 pounds is not going to stop losing weight on a 1200 calorie diet. It may slow but it will continue.

What we term “Reverse Dieting”, has always been a tool that we use more commonly referred to as “coaching the client to eat better". When we find clients on extreme diets, we recommend they reduce the caloric deficit by increasing calories to make the changes sustainable and keep them from hormone or other chemical imbalances that then affect everything, the worst of which is the depressed mental attitude that makes exercise and dieting even harder. But we keep some reasonable amount of caloric deficit if we wish to continue the weight loss.

The reason Reverse Dieting appears to work is that you gave the client both a healthy diet that indeed may be helping them increase or optimize their chemistry and metabolism and you have now given them an uncontrolled 3rd party factor to blame it on, a proverbial scape goat to save face and begin a new start without calling them out on their previous diet. The mental benefits of this and the incentive to the client, not to mention the trust relationship built with the Coach should not be underestimated. Obesity has been an emotional burden for many people. It is a multi-factor complex issue of what we call the Art of Science. Science in the lab is straight forward but it is an art to apply it on humans with emotions, behaviors and habits that don't follow the same straight line in the lab.

Control

Maintenance Diet

To avoid this issue from recurring in the future we need to start exploring what the quality of a nutritional diet can do to the client’s ability to lose weight and sustain a maintenance plan vs wasting time believing that someone’s metabolism was possibly negatively affected by 1000+ calories daily which isn’t supported to that level within the scientific literature.

https://youtu.be/hgGe8F23OeA

It should be noted that during a period of weight loss the body is naturally shrinking and as a result so it the metabolism. This is not a sign of any metabolic abnormality but rather a natural effect of metabolism staying in sync with body mass. As such it is prudent to continually test or recalibrate RMR and adjust caloric intake accordingly to maintain weight loss.

Best practices to maintain weight loss is to revisit various steps of the initial process and develop a plan for when the variations of the key tracking variables become to great to be able to maintain the initial results.

• Retest and recalibrate metabolic needs and set maintenance level targets for caloric intake.
• Create an acceptable plan of action for when the client knows they have temporarily veered off the targets set so they have a preemptive plan to return to the regular program.
• Develop a plan to deliberately get off track when life events require deviations and make that part of the regular plan.
• Although an obsession with weighing can be detrimental, it is an excellent early indicator of a return to old habits. Set a percentage of 3-5% over a 1-2 week period to avoid panicking about daily fluid fluctuations.
• Retest metabolism regularly if you have access to a metabolic cart, otherwise recalculate RMR based on current variables.
• Perform regular body composition assessments and target an acceptable range of body fat that will keep the client within normal healthy percentages with a preprogrammed plan of action for intervention should they break through an upper limit.
• Set a minimum weekly level and type of physical movement that will be required for the new maintenance weight. Develop a tracking system to be able to intervene if movement goals are not being met.
• Every quarter the client should journal their nutritional habits for a 3-day period for Practitioner review. Caloric or quality intake that exceeds or doesn't meet the targets set upon reaching the goal weight should be discussed and substitutions and solutions to remain on track should be reviewed and agreed upon.
• Develop regular check-ins especially during life changing events or seasons such as holidays.

Note: Chronic undereating can be far different than a diagnosed disorder such as anorexia nervosa. Extreme cases of eating disorders can impact metabolism to the point of disrupting chemical requirements required to stay alive. Metabolic issues related to extreme starvation are outside the scope of normal health coaching and should not be interpreted to be similar to working with clients that are on low or very low calorie diets for extended periods but are otherwise healthy. When their is any question that the client's health may be impacted by their chronic eating habits, the Client should be referred out to a qualified licensed professional before moving forward in any health plan.

Scientific References

Below are several conservative examples of many research articles on this topic as it comes up often and is part of and one reason Coaches and Clients confuse how CICO (Calories In Calories Out) works as well. Note that this is but one variable affecting the CICO equation, not negating it.

1. Resting metabolic rate of obese patients under very low calorie ketogenic diet
Gomez-Arbelaez, D., Crujeiras, A. B., Castro, A. I., Martinez-Olmos, M. A., Canton, A., Ordoñez-Mayan, L., Sajoux, I., Galban, C., Bellido, D., & Casanueva, F. F. (2018). Resting metabolic rate of obese patients under very low calorie ketogenic diet. Nutrition & Metabolism, 15(1). https://doi.org/10.1186/s12986-018-0249-z

Abstract
Background
The resting metabolic rate (RMR) decrease, observed after an obesity reduction therapy is a determinant of a short-time weight regain. Thus, the objective of this study was to evaluate changes in RMR, and the associated hormonal alterations in obese patients with a very low-calorie ketogenic (VLCK)-diet induced severe body weight (BW) loss.

Method
From 20 obese patients who lost 20.2 kg of BW after a 4-months VLCK-diet, blood samples and body composition analysis, determined by DXA and MF-Bioimpedance, and RMR by indirect calorimetry, were obtained on four subsequent visits: visit C-1, basal, initial fat mass (FM) and free fat mass (FFM); visit C-2, − 7.2 kg in FM, − 4.3 kg in FFM, maximal ketosis; visit C-3, − 14.4 kg FM, − 4.5 kg FFM, low ketosis; visit C-4, − 16.5 kg FM, − 3.8 kg FFM, no ketosis. Each subject acted as his own control.

Results
Despite the large BW reduction, measured RMR varied from basal visit C-1 to visit C-2, − 1.0%; visit C-3, − 2.4% and visit C-4, − 8.0%, without statistical significance. No metabolic adaptation was observed. The absent reduction in RMR was not due to increased sympathetic tone, as thyroid hormones, catecholamines, and leptin were reduced at any visit from baseline. Under regression analysis FFM, adjusted by levels of ketonic bodies, was the only predictor of the RMR changes (R2 = 0.36; p < 0.001).

Conclusion
The rapid and sustained weight and FM loss induced by VLCK-diet in obese subjects did not induce the expected reduction in RMR, probably due to the preservation of lean mass.
https://nutritionandmetabolism.biomedcentral.com/articles/10.1186/s12986-018-0249-z

2. Effects of a low-calorie diet on resting metabolic rate and serum tri-iodothyronine levels in obese children
Kiortsis , D. N., Turpin, G., & Durack, I. (n.d.). Effects of a low-calorie diet on resting metabolic rate and serum tri-iodothyronine levels in obese children. European journal of pediatrics. Retrieved June 24, 2022, from https://pubmed.ncbi.nlm.nih.gov/10378389/ 

Here we see a 10% decline in RMR in obese children on a low calorie diet.
https://pubmed.ncbi.nlm.nih.gov/10378389/

3. Effects of a very-low-calorie diet and physical-training regimens on body composition and resting metabolic rate in obese females
Donnelly, J. E., Pronk, N. P., Jacobsen, D. J., Pronk, S. J., & Jakicic, J. M. (1991, July 1). Effects of a very-low-calorie diet and physical-training regimens on body composition and resting metabolic rate in obese females. OUP Academic. Retrieved June 24, 2022, from https://academic.oup.com/ajcn/article-abstract/54/1/56/4691082 

Obese woman had a 7-12% decline in RMR after being on a very low-calorie diet of 2184 KJ or about 500 calories. The average RMR in females is about 1400 calories so a range of 98 - 168 calories. Remember that RMR makes up approximately 70% of most individuals energy expenditures so a 1400 RMR might translate into 2000 total calories before formal exercise. So even if they were on a sustained low-calorie diet of say 1200 calories, their metabolism would still be at 1800 for the day creating a 600 calorie deficit.
https://academic.oup.com/ajcn/article-abstract/54/1/56/4691082

4. Leucine, glucose, and energy metabolism after 3 days of fasting in healthy human subjects
Nair, K. S., Woolf, P. D., Welle, S. L., & Matthews, D. E. (1987, October 1). Leucine, glucose, and energy metabolism after 3 days of fasting in healthy human subjects. OUP Academic. Retrieved June 24, 2022, from https://academic.oup.com/ajcn/article-abstract/46/4/557/4694572 

Six young men fasted for 3 days. RMR decreased 8%. The average male RMR is approximately 1600 calories and as such would infer a decrease of 128 calories. If their total energy expenditures were 2300 calories and their RMR dropped 128 they would still lose weight consuming anything under approximately 2200 calories.
https://academic.oup.com/ajcn/article-abstract/46/4/557/4694572

5. The effect of varying carbohydrate content of a very-low-caloric diet on resting metabolic rate and thyroid hormones
Mathieson, R. A., Walberg, J. L., Gwazdauskas, F. C., Hinkle, D. E., & Gregg, J. M. (2004, April 2). The effect of varying carbohydrate content of a very-low-caloric diet on resting metabolic rate and thyroid hormones. Metabolism. Retrieved June 24, 2022, from https://www.sciencedirect.com/science/article/abs/pii/0026049586901265 

This is a very interesting study. Two groups of women were both put on very low-calorie diets for 28 days.  One group was very low carbohydrate while the other was high carbohydrate, but the caloric intakes were very low in total in both cases by adjusting other macronutrients. Progressive decreases in RMR were noted during treatment (12.4% for Low Carb and 20.8% for High Carb), but values were not significantly lower than baseline until week 3 of the very low calories diet. A 20% decrease in RMR can start having more of an impact on one's ability to lose weight on a very low-calorie diet but still only about a 250 calorie affect. So, weight loss might slow but would continue. Couple this with the fact that most individuals don't do low calorie high carb unless they are performing athletically requiring a lot of training and even then, we see more moderate carb consumption as opposed to low carb to keep energy levels high.
https://www.sciencedirect.com/science/article/abs/pii/0026049586901265

6. Effects of Resistance vs. Aerobic Training Combined With an 800 Calorie Liquid Diet on Lean Body Mass and Resting Metabolic Rate
Bryner, R. W., Ullrich, I. H., Sauers, J., Donley, D., Hornsby, G., Kolar, M., & Yeater, R. (1999). Effects of resistancevs.aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate. Journal of the American College of Nutrition, 18(2), 115–121. https://doi.org/10.1080/07315724.1999.10718838 

Here is an interesting study on the effects of an 800-calorie liquid diet while continuing resistance or aerobic training. Conclusion: The addition of an intensive, high volume resistance training program resulted in preservation of Lean Bodyweight and RMR during weight loss with a Very Low-Calorie Diet.
https://www.tandfonline.com/doi/abs/10.1080/07315724.1999.10718838

7. The Metabolic Responses to Starvation and Refeeding in Adolescents with Anorexia Nervosa
Schebendach JE, Golden NH, Jacobson MS, Hertz S, Shenker IR. The metabolic responses to starvation and refeeding in adolescents with anorexia nervosa. Annals of the New York Academy of Sciences. 1997 May;817:110-119. DOI: 10.1111/j.1749-6632.1997.tb48200.x. PMID: 9239182.

Here is one of the most extreme cases I have seen in research performed on patients with Anorexia nervosa, often simply called anorexia. Individuals diagnosed with this disease severely restrict the amount of food they eat or force themselves to vomit after eating or by misusing laxatives, diet aids, diuretics or enemas.

In this research 50 females were admitted to a hospital for treatment and were initially tested using indirect calorimetry to ascertain their resting metabolic rate which ranged from 17% to almost 40% lower than predicted formulas. The range of difference was broad and may be accounted for due to the fact that the baseline RMR for some of these individuals under normal healthy conditions may have been significantly lower than predicted norms.

That being said, the average RMR for an averaged size female is approximately 1400 calories. If resting metabolic rate was affected by as much as 40% the metabolic damage inflicted would reduce their RMR to 840 calories. This does not include calories burned during normal daily activities or any extraordinary exercise. When adding these items to the total energy expenditure the totals caloric expenditures could easily exceed 1000 calories a day in the worst of cases. As such individuals eating less than 1000 calories would still be losing weight.

The average metabolic damage caused by one of the worst eating disorders was approximately 18% across all patients. Performing that same metabolic math would create a 288 calorie reduction to 1152 calories per day. When adding back expended energy due to daily activities, total expenditures would likely exceed 1400-1500 calories. Again, an individual eating less than this level would continue losing weight irrespective of the fact that metabolism is temporarily negatively impacted.
https://europepmc.org/article/med/9239182

8. Energy balance measurement: when something is not better than nothing. International journal of obesity (2005)
Dhurandhar, N. V., Schoeller, D., Brown, A. W., Heymsfield, S. B., Thomas, D., Sørensen, T. I., Speakman, J. R., Jeansonne, M., Allison, D. B., & Energy Balance Measurement Working Group (2015). 39(7), 1109–1113. https://doi.org/10.1038/ijo.2014.199

An extremely interesting article on how self reported energy intake is underreported by hundreds of calories. Specifically, they state that the NHANES surveys may underreport energy intake as much as 800 kcal/d. The National Health and Nutrition Examination Survey (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. The researchers assert that the inaccuracies of self reported energy intake are so bad that it damages their ability to perform accurate scientific research thus causing them to draw conclusions that may do more damage than good. The Energy Balance Measurement Working Group stated that self-reports are "so poor that they are wholly unacceptable for scientific research on energy intake and physical activity energy expenditure".

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4430460/

9. Dietary underreporting by obese individuals--is it specific or non-specific?
Heitmann BL, Lissner L. Dietary underreporting by obese individuals--is it specific or non-specific? BMJ. 1995 Oct 14;311(7011):986-9. doi: 10.1136/bmj.311.7011.986. PMID: 7580640; PMCID: PMC2550989.

This research found that the degree of obesity was positively associated with underreporting of total energy and protein, whereas compared with total energy reported, protein was overreported by the obese subjects. It noted that dietary underreporting varies with the type of foods consumed, age, gender, smoking habits, education, social class, dietary restraint, the body mass index of respondent, and other life-stage factors.

https://pubmed.ncbi.nlm.nih.gov/7580640/