What You Need To Know About Metabolic Adaptation

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As we all know, body composition is a critical factor in many sports. Whether you’re going for a bodybuilding pro card, dropping fat to improve your speed, or dropping a weight class to seek out that record-setting squat, effective weight loss strategies will be key to your success.

A few months ago, I published a paper in the Journal of the International Society of Sports Nutrition (20). The paper was a literature review discussing the metabolic consequences of dieting, with an emphasis on how this literature pertains to athletes. If you read the paper and you’re a person with somewhat “normal” interests, you were probably bored to tears. So, the purpose of this article is to briefly summarize that huge wall of text in JISSN.

What is metabolic adaptation?

As JTS readers are well aware, the human body is resilient. You may have noticed that you’ve been able to add more and more plates to that bar on your back, despite the rigorous stress you’ve been putting your body through day in and day out.

When people talk about obesity, you sometimes hear about the thrifty gene hypothesis. The general idea is that humanity evolved to favor a genotype that allows us to store excess calories as fat, primarily as a survival mechanism. Essentially, we’re able to save up energy during times of feasting, just in case we encounter a famine later.

I like to think of metabolic adaptation as the other side of the thrifty gene hypothesis— instead of talking about what happens during the “feast,” metabolic adaptation addresses the “famine.”

During weight loss, two things happen: We impose a caloric deficit, either by increasing exercise or decreasing food intake, and we begin to lose body mass (hopefully most of this is fat mass, rather than lean mass). These are both indicators that energy supply is low, and the body adapts accordingly. In short, these adaptations may include (13, 20):

  • Increased mitochondrial efficiency (less calories burned to produce the same amount of ATP) (1, 7)

  • Decreased energy expenditure (metabolic rate) (5, 17, 18)

  • Elevations in hormones that promote catabolism and hunger, with decreased hormones that promote anabolism, energy expenditure, and satiety (15, 19)


What are the effects of these adaptations?

As you can imagine, these adaptations directly oppose your weight loss goals. Changes in mitochondrial efficiency and energy expenditure decrease your energy deficit, which slows weight loss. Further, the hormonal changes make it difficult to retain lean mass, threaten energy levels and general mood state, and increase hunger. One particularly unfavorable result pertains to the sex hormones; many natural male bodybuilders encounter symptoms of low testosterone late into contest prep (14, 19), and amenorrhea is commonly experienced by female athletes (10).

The effects of these adaptations also extend beyond the weight loss phase. Let’s say you made it down to that weight class you were shooting for, or you’ve achieved a stage-ready level of body fat.

Now what?

Even after you’ve lost the weight, research has indicated that many of these adaptations persist as you try to maintain your new body weight (12, 17). These adaptations, which have decreased your metabolic rate and increased hunger, also set you up for a huge rebound. If you don’t practice some restraint after the diet, rapid weight regain is common.

Further, research has shown that the weight gained is this period is preferentially stored as fat (21), and that adipocyte hyperplasia (the addition of new fat cells) may occur (9). This can lead to a phenomenon known as post-starvation obesity (21) or body fat overshooting (6); in this scenario, the dieter actually regains more fat than they lost during the diet. Ultimately, this diminishes the progress made throughout the diet, and makes future dieting attempts more difficult.

Common misconceptions about metabolic adaptation

Metabolic adaptation has become a fairly popular topic of discussion amongst fitness coaches and competitors. As such, a number of common misconceptions have surfaced. A few of these misconceptions include:

1. Metabolic adaptation can make weight loss impossible, or can make you gain weight despite a caloric deficit

Metabolic adaptation does not refer to some supernatural circumvention of the laws of thermodynamics— these adaptations simply serve to decrease energy expenditure. So, the energy deficit becomes smaller, and weight loss may eventually stall as energy expenditure approaches energy intake. At this point, weight loss can continue if more exercise is added, or if caloric intake is reduced. But this becomes very tricky when exercise volume is already high, and caloric intake is already low. In some cases, you do reach a limit where it’s no longer advisable, practical, or healthy to continue making extreme adjustments.

2. These adaptations are a dire problem

Not so.

These are adaptations that naturally accompany weight loss and address the “energy crisis” your body is facing in a caloric deficit, especially when you start to become very lean. A really dire problem would be if these adaptations didn’t occur, and the human body was more susceptible to starvation. If that were the case, our evolutionary history might tell a slightly different story.

3. These adaptations are indicative of improper dieting

Again, this is not 100% true. To some degree, these adaptations are to be expected with calorie reduction and weight loss. Even with the most optimized weight loss strategies, you will still expect these adaptations to occur to some extent. However, it is likely that they are exacerbated by improper strategies, so they can likely be attenuated by a more ideal approach to weight loss.

What can be done to avoid these adaptations?

Unfortunately it is unlikely that these adaptations can be avoided entirely. However, you can likely minimize them by employing proper dieting techniques.

Obviously, sufficient protein is important. It has the highest thermic effect of any macronutrient and is highly satiating (16); further, it will assist in the retention of lean mass and metabolic rate (11). The same can be said for participation in a structured, well-designed resistance training program (2). But you’re reading an article on the JTS website, so you’re probably taking care of those already.

Theoretically, the magnitude of these adaptations is likely related to the size of the energy deficit (20)— a larger deficit signifies a more urgent energy crisis. So, it is advised to impose the smallest possible deficit that yields appreciable weight loss, and to establish a relatively slow rate of weight loss (3). When weight loss begins to stall, make modest, conservative adjustments to increase the energy deficit, and approach the diet in a step-wise fashion with incremental, periodic adjustments.

Unfortunately, cardio often becomes a necessity when trying to achieve very low body fat. However, as a general rule, it may be best to keep cardio as minimal as possible throughout the weight loss phase. Not only can cardio potentially cut into your recovery from resistance training, but the interference effect of concurrent training may be counterproductive. When cardio is necessary, it may be best to avoid higher-impact modalities, long durations, and low intensities; a mix of moderate intensity cardio and high-intensity intervals on a stationary bike are solid choices (22).

Periodic carbohydrate refeeds are currently very popular in the world of physique sports. Theoretically, they may help to influence metabolic rate and satiety by temporarily elevating leptin (4), but more research is needed on this topic. Reverse dieting is another popular strategy employed by physique athletes. While there is little relevant data on this strategy, it could theoretically help with maintaining weight loss. While a bodybuilder should not aim to stay at stage weight for an extended period of time, this strategy could help competitors stay within striking distance during their offseason, and is likely to prevent body fat overshooting in the post-diet period. For the general population, reverse dieting may help them maintain a large percentage of their weight loss, but this is speculative and research on the topic is needed. It is important to emphasize that reverse dieting does not mean you need to keep a caloric deficit beyond the intended weight loss period— it simply refers to gradually increasing calories, as opposed to a massive, drastic caloric surplus.

For more practical strategies for weight loss, refer to a recent (excellent) paper by Helms, Aragon & Fitschen (8).


There are certain metabolic adaptations that accompany energy restriction and weight loss. These adaptations, which are likely survival mechanisms to avoid starvation, generally serve to increase efficiency and reduce the caloric deficit. While metabolic adaptation is not some dire, perilous occurrence, it certainly opposes weight loss goals. Although metabolic adaptation is not entirely avoidable, a well-planned approach to training and nutrition can likely minimize these adaptations and promote more successful weight loss. By employing sound weight-loss strategies, you can lose the weight more effectively, increase the likelihood of maintaining weight loss, and set yourself up for improved body composition and performance down the road.

About the author:

Eric Trexler is a strength coach, powerlifter, and natural bodybuilder, and serves as the Director of Research and Education for INOV8 Elite Performance. He is also a graduate student and active researcher, conducting exercise and nutrition research at the University of North Carolina at Chapel Hill.



1.    Bevilacqua L, Ramsey JJ, Hagopian K, Weindruch R, and Harper ME. Effects of short- and medium-term calorie restriction on muscle mitochondrial proton leak and reactive oxygen species production. American journal of physiology Endocrinology and metabolism 286: E852-861, 2004.

2.    Bryner RW, Ullrich IH, Sauers J, Donley D, Hornsby G, Kolar M, and Yeater R. Effects of resistance vs. 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: 115-121, 1999.

3.    Chaston TB, Dixon JB, and O’Brien PE. Changes in fat-free mass during significant weight loss: a systematic review. International journal of obesity 31: 743-750, 2007.

4.    Dirlewanger M, di Vetta V, Guenat E, Battilana P, Seematter G, Schneiter P, Jequier E, and Tappy L. Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects. International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity 24: 1413-1418, 2000.

5.    Doucet E, St-Pierre S, Almeras N, Despres JP, Bouchard C, and Tremblay A. Evidence for the existence of adaptive thermogenesis during weight loss. The British journal of nutrition 85: 715-723, 2001.

6.    Dulloo AG, Jacquet J, and Girardier L. Poststarvation hyperphagia and body fat overshooting in humans: a role for feedback signals from lean and fat tissues. The American journal of clinical nutrition 65: 717-723, 1997.

7.    Esterbauer H, Oberkofler H, Dallinger G, Breban D, Hell E, Krempler F, and Patsch W. Uncoupling protein-3 gene expression: reduced skeletal muscle mRNA in obese humans during pronounced weight loss. Diabetologia 42: 302-309, 1999.

8.    Helms E, Aragon A, and Fitschen P. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 11: 20, 2014.

9.    Jackman MR, Steig A, Higgins JA, Johnson GC, Fleming-Elder BK, Bessesen DH, and MacLean PS. Weight regain after sustained weight reduction is accompanied by suppressed oxidation of dietary fat and adipocyte hyperplasia. American journal of physiology Regulatory, integrative and comparative physiology 294: R1117-1129, 2008.

10.    Lagowska K, Kapczuk K, Friebe Z, and Bajerska J. Effects of dietary intervention in young female athletes with menstrual disorders. Journal of the International Society of Sports Nutrition 11: 21, 2014.

11.    Layman DK, Boileau RA, Erickson DJ, Painter JE, Shiue H, Sather C, and Christou DD. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. The Journal of nutrition 133: 411-417, 2003.

12.    Leibel RL and Hirsch J. Diminished energy requirements in reduced-obese patients. Metabolism: clinical and experimental 33: 164-170, 1984.

13.    Maclean PS, Bergouignan A, Cornier MA, and Jackman MR. Biology’s response to dieting: the impetus for weight regain. American journal of physiology Regulatory, integrative and comparative physiology 301: R581-600, 2011.

14.    Maestu J, Eliakim A, Jurimae J, Valter I, and Jurimae T. Anabolic and catabolic hormones and energy balance of the male bodybuilders during the preparation for the competition. Journal of strength and conditioning research / National Strength & Conditioning Association 24: 1074-1081, 2010.

15.    Maestu J, Jurimae J, Valter I, and Jurimae T. Increases in ghrelin and decreases in leptin without altering adiponectin during extreme weight loss in male competitive bodybuilders. Metabolism: clinical and experimental 57: 221-225, 2008.

16.    Paddon-Jones D, Westman E, Mattes RD, Wolfe RR, Astrup A, and Westerterp-Plantenga M. Protein, weight management, and satiety. The American journal of clinical nutrition 87: 1558S-1561S, 2008.

17.    Rosenbaum M, Hirsch J, Gallagher DA, and Leibel RL. Long-term persistence of adaptive thermogenesis in subjects who have maintained a reduced body weight. The American journal of clinical nutrition 88: 906-912, 2008.

18.    Rosenbaum M and Leibel RL. Adaptive thermogenesis in humans. International journal of obesity 34 Suppl 1: S47-55, 2010.

19.    Rossow LM, Fukuda DH, Fahs CA, Loenneke JP, and Stout JR. Natural bodybuilding competition preparation and recovery: a 12-month case study. International journal of sports physiology and performance 8: 582-592, 2013.

20.    Trexler ET, Smith-Ryan AE, and Norton LE. Metabolic adaptation to weight loss: implications for the athlete. Journal of the International Society of Sports Nutrition 11: 7, 2014.

21.    Weyer C, Walford RL, Harper IT, Milner M, MacCallum T, Tataranni PA, and Ravussin E. Energy metabolism after 2 y of energy restriction: the biosphere 2 experiment. The American journal of clinical nutrition 72: 946-953, 2000.

22.    Wilson JM, Marin PJ, Rhea MR, Wilson SM, Loenneke JP, and Anderson JC. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Journal of strength and conditioning research / National Strength & Conditioning Association 26: 2293-2307, 2012.

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