A Scientific Overview of the Concept of ‘Starvation Mode’

You've probably heard of starvation mode, right? But what is the scientific basis of this concept? And what can we do practically to avoid it?

A Scientific Overview of the Concept of ‘Starvation Mode’

By Joseph Agu | Reading Time: 11 minutes |


To ensure that we’re on the same page from the get go, it’s important to outline what we mean when speaking of ‘starvation mode’. Starvation mode is a nontechnical term that describes a decrease in energy expenditure associated with dieting.

The scientific term for this metabolic adaptation is called ‘adaptive thermogenesis’ (AT). AT can be defined as the changes in resting and non-resting energy expenditure (REE and nREE) that are independent of changes in fat-free mass (FFM) and body composition.[1]Müller, MJ. / Bosy-Westphal, A. (2013): Adaptive thermogenesis with weight loss in humans. In: Obesity. URL: https://onlinelibrary.wiley.com/doi/full/10.1002/oby.20027.[2]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.

A Scientific Overview of the Concept of ‘Starvation Mode’

Components of Energy Metabolism

Resting energy expenditure – sometimes referred to as basal metabolic rate, though they technically aren’t exactly the same thing – is the amount of energy needed to keep all bodily functions working at complete rest, and typically represents around 60% of an individual’s total energy expenditure.[3]Müller, MJ. / Enderle, J. / Bosy-Westphal, A. (2016): Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. In: Curr Obes Rep. URL:  https://www.ncbi.nlm.nih.gov/pubmed/27739007. The thermic effect of food (TEF) – also known as diet-induced thermogenesis – is the energy required for digestion, absorption, and disposal of ingested nutrients, and accounts for around 10-15% of total energy expenditure.[4]Levine, JA. (2002): Non-exercise activity thermogenesis (NEAT). In: Best Pract Res Clin Endocrinol Metab. URL: https://www.sciencedirect.com/science/article/abs/pii/S1521690X02902277. The remaining 25-30% of daily energy expenditure is made up of exercise activity thermogenesis (EAT) and non-exercise activity thermogenesis (NEAT).[5]Levine, JA. (2002): Non-exercise activity thermogenesis (NEAT). In: Best Pract Res Clin Endocrinol Metab. URL: https://www.sciencedirect.com/science/article/abs/pii/S1521690X02902277.

Components of Energy Metabolism

The components of our energy metabolism (TDEE). (Graphic Source: Trexler et al., 2014)

As the name suggests, EAT includes all forms of formal exercise (e.g. weight training, running, cycling, etc.). NEAT, on the other hand, includes everything else that uses more energy than complete rest and isn’t strictly exercise (e.g. sitting, standing, fidgeting, walking to work, driving, etc.). For many westerners, EAT is negligible, meaning that NEAT makes up the vast majority of their nREE. For us active folk, the higher the quantity of exercise undertaken, the larger the contribution of EAT to total energy expenditure becomes, meaning that the contribution of REE to total expenditure decreases.

Our bodies don’t really like change

Adaptive thermogenesis occurs during over feeding as well as underfeeding. During underfeeding/dieting, AT is directed towards energy conservation in a biological effort to defend losses of body mass. This is great for survival, but not so great when we, or our clients, deliberately want to lose weight. Conversely, during overfeeding, AT is directed towards energy dissipation. For example, if someone were to eat 500 kcals per day over their maintenance energy requirements, they might only store 250 of those Calories; the rest being dissipated due to an increase in nREE, predominantly NEAT.[6]Apolzan, JW., et al. (2014): Effects of weight gain induced by controlled overfeeding on physical activity. In: Am J Physiol Endocrinol Metab. URL: https://www.ncbi.nlm.nih.gov/pubmed/25294214.[7]Leibel, RL. / Rosenbaum, M. / Hirsch, J. (1995): Changes in energy expenditure resulting from altered body weight. In: N Engl J Med. URL: https://www.ncbi.nlm.nih.gov/pubmed/7632212.[8]Tremblay, A., et al. (1992): Overfeeding and energy expenditure in humans. In: Am J Clin Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/1415004.

Inter-individual variance in the rest-related (=ΔREEadj FFM) and non-rest-related (ΔAEEadj FFM) compartment of adaptive thermogenesis (AT) during a 3-week controlled underfeeding (at -50% of energy demand, here in green) and a 2-week overfeeding (at +50% of energy demand, here in red) in 31 healthy and normal weight young men. For original data see Müller et al. (2015). The participants were ranked according to their REE value before the intervention (upper panel). After an adjustment for fat-free mass, there were no inter-individual differences in REE measurement before the weight cycle. Average changes in weight loss or weight gain are shown on the right side. An adaptation of thermogenesis only occurred during underfeeding. REE = rest energy consumption; AEE = activity-related energy consumption; FFM = fat-free mass.

Inter-individual variance in the rest-related (=ΔREEadj FFM) and non-rest-related (ΔAEEadj FFM) compartment of adaptive thermogenesis (AT) during a 3-week controlled underfeeding (at -50% of energy demand, here in green) and a 2-week overfeeding (at +50% of energy demand, here in red) in 31 healthy and normal weight young men. For original data see Müller et al. (2015). The participants were ranked according to their REE value before the intervention (upper panel). After an adjustment for fat-free mass, there were no inter-individual differences in REE measurement before the weight cycle. Average changes in weight loss or weight gain are shown on the right side. An adaptation of thermogenesis only occurred during underfeeding. REE = rest energy consumption; AEE = activity-related energy consumption; FFM = fat-free mass. (Graphic Source: Müller et al., 2016)

Adaptive thermogenesis during overfeeding varies massively from person to person, and seemingly explains the notion of the classic ‘hard gainer’ (i.e. someone that, despite their best efforts, struggles to gain body mass).[9]Levine, JA. (2002): Non-exercise activity thermogenesis (NEAT). In: Best Pract Res Clin Endocrinol Metab. URL: https://www.sciencedirect.com/science/article/abs/pii/S1521690X02902277.[10]Levine, JA. / Eberhardt, NL. / Jensen, MD. (1999): Role of nonexercise activity thermogenesis in resistance to fat gain in humans. In: Science. URL: https://www.ncbi.nlm.nih.gov/pubmed/9880251.

In the rest of the article, we will take a closer look at the literature on AT during dieting conditions, and see what practical takeaways we can use to better serve our clients.

Various components of energy consumption and thermogenesis (heat production). DIT (Diet-Induced Thermogenesis) refers to the postprandial increase in energy consumption resulting as the cost of macronutrient processing (obligatory food-related thermogenesis) plus an optional component, which is defined as the postprandial increase in energy consumption during the processing of excessive energy (specific dynamic activity). Adaptive thermogenesis (AT) is defined as the reduction of the metabolic rate after adaptation of body mass and body composition due to food and environment. Adaptive thermogenesis has a rest energy expenditure component (REE) and a non-rest energy expenditure component (nREE). Modified according to Tseng et al (2011).

Various components of energy consumption and thermogenesis (heat production). DIT (Diet-Induced Thermogenesis) refers to the postprandial increase in energy consumption resulting as the cost of macronutrient processing (obligatory food-related thermogenesis) plus an optional component, which is defined as the postprandial increase in energy consumption during the processing of excessive energy (specific dynamic activity). Adaptive thermogenesis (AT) is defined as the reduction of the metabolic rate after adaptation of body mass and body composition due to food and environment. Adaptive thermogenesis has a rest energy expenditure component (REE) and a non-rest energy expenditure component (nREE). Modified according to Tseng et al (2011). (Graphic Source: Müller & Bosy-Westphal, 2013)

History of ‘Starvation Mode’

In science, adaptive thermogenesis is not a new concept as published accounts of its existence were being discussed over 100 years ago.[11]Gulick, A. (1922): A study of weight regulation in the adult human body during overnutrition. In: Am J Physiol. URL: https://www.ncbi.nlm.nih.gov/pubmed/8521172. In 1950, Ancel Keys and colleagues published the very first quantitative description of AT in humans in the famous ‘Minnesota Semi-starvation Experiment’. [12]Keys, A., et al. (1950): The Biology of Human Starvation. In: The University of Minnesota Press. URL: https://psycnet.apa.org/record/1951-02195-000. Anecdotally, people have been struggling to lose weight and keep it off for as long as we’ve desired to do so. In this fitness industry, AT has sprung to popularity over the last half decade, particularly among physique competitors. There are numerous reports of female competitors not losing weight despite consuming an extremely low number of Calories (i.e. 700-900 kcal/day), combined with high volumes of cardio (i.e. >2 hours/day), all on top of their weight training. Such phenomenon has given birth to the concept of ‘metabolic damage’, which is essentially a non-scientific term to describe a natural metabolic adaptation that is encompassed by AT.[13]Trexler, ET. / Smith-Ryan, AE. / Norton, LE. (2014): Metabolic adaptation to weight loss: implications for the athlete. In: J Int Soc Sports Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/24571926.

Though AT is undoubtedly occurring in the majority of these scenarios, it’s a physiological impossibility that it’s occurring to an extent that explains a lack of fat loss in the presence of such a restricted energy intake combined with high energy expenditure. Instead, something else must be going on. That something typically involves cortisol-induced water retention and underreporting of food intake, or both.[14]Hall, JE. (2015): Guyton and Hall Textbook of Medical Physiology. Saunders. Available at Amazon.com.[15]Rennie, KL. / Coward, A. / Jebb, SA. (2007): Estimating under-reporting of energy intake in dietary surveys using an individualised method. In: Br J Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/17433123.

Underreporting is the (un)arbitrary misappropriation of energy intake. The actual food intake is many times higher (20-30% of the energy requirement and more) than the stated energy intake, whereby the body composition (Slim Vs. Thick) seems to play an important role. It is conceivable, for example, that overweight people often indicate a lower calorie intake than is true. The table shows the estimated under-reporting, based on weight status, in 1,551 healthy individuals (white bars) and 1,133 sick or dieting individuals (black bars), based on data from the National Diet and Nutrition Survey.

Underreporting is the (un)arbitrary misappropriation of energy intake. The actual food intake is many times higher (20-30% of the energy requirement and more) than the stated energy intake, whereby the body composition (Slim Vs. Thick) seems to play an important role. It is conceivable, for example, that overweight people often indicate a lower calorie intake than is true. The table shows the estimated under-reporting, based on weight status, in 1,551 healthy individuals (white bars) and 1,133 sick or dieting individuals (black bars), based on data from the National Diet and Nutrition Survey. (Graphic Source: Rennie et al., 2007)

How much do we adapt?

In the classic ‘Minnesota Semi-Starvation Experiment’, conscientious objectors were subjected to semi-starvation to study the effects of famine during WW2.[16]Keys, A., et al. (1950): The Biology of Human Starvation. In: The University of Minnesota Press. URL: https://psycnet.apa.org/record/1951-02195-000. For 24 weeks, these 32 men were required to consume 50% of their maintenance energy requirements and to complete 15 hours of work tasks and 22 miles of walking each week. Over the course of the 24 weeks, subjects lost one-quarter of their body mass – reaching the near-limits of human leanness – and experienced a 40% reduction in basal metabolic rate. Of this 40% reduction, 25% was accounted for by a reduction in body mass. The remaining 15% reduction in basal metabolism was due to an adaptive component. That is, a reduction that cannot be explained by changes in fat and lean mass.

These results are consistent with the weight of the literature, as highlighted by Rosenbaum and Leibel in their 2010 review on the topic of AT.[17]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.  On average, research demonstrates that a 10% or greater reduction in body mass in lean or obese people accompanies a 20-25% decline in total energy expenditure. Of this 20-25%, 10-15% is due to AT.[18]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.[19]Leibel, RL. / Rosenbaum, M. / Hirsch, J. (1995): Changes in energy expenditure resulting from altered body weight. In: N Engl J Med. URL: https://www.ncbi.nlm.nih.gov/pubmed/7632212.[20]Weigle, DS., et al. (1988): Weight loss leads to a marked decrease in nonresting energy expenditure in ambulatory human subjects. In: Metabolism. URL: https://www.ncbi.nlm.nih.gov/pubmed/3173112. This would represent a downward shift in metabolic rate of around 300-400 kcal per day, though greater adaptations are possible with more extreme weight loss,[21]Fothergill, E., et al. (2016): Persistent metabolic adaptation 6 years after ‘The Biggest Loser’ competition. In: Obesity. URL: https://www.ncbi.nlm.nih.gov/pubmed/27136388. in which further adaptations are almost exclusively in the form of nREE (i.e. NEAT).[22]Rosenbaum, M. / Leibel, RL. (2016): Models of energy homeostasis in response to maintenance of reduced body weight. In: Obesity. URL: https://www.ncbi.nlm.nih.gov/pubmed/27460711.

Daily energy expenditure in 28 overweight individuals (men & women) before and after a 3-4 month diet (average weight loss: 23.2% ± 9.4%). 24-h EE = energy expenditure within a 24-hour period; RMR = basal metabolism rate; NR EE = non-rest energy expenditure.

Daily energy expenditure in 28 overweight individuals (men & women) before and after a 3-4 month diet (average weight loss: 23.2% ± 9.4%). 24-h EE = energy expenditure within a 24-hour period; RMR = basal metabolism rate; NR EE = non-rest energy expenditure. (Graphic Source: Weigle et al., 1988)

These reductions in resting energy expenditure and NEAT are further compounded by improvements in the chemo-mechanical efficiency of muscle (i.e. the energy needed to contract the muscles to perform a set amount of work). For example, the maintenance of a 10% reduced body weight is associated with an approximate 20% increase in skeletal muscle work efficiency during low-intensity exercise.[23]Goldsmith, R., et al. (2010): Effects of experimental weight perturbation on skeletal muscle work efficiency, fuel utilization, and biochemistry in human subjects. In: Am J Physiol Regul Integr Comp Physiol. URL: https://www.ncbi.nlm.nih.gov/pubmed/19889869.[24]Rosenbaum, M., et al. (2003): Effects of experimental weight perturbation on skeletal muscle work efficiency in human subjects. Am J Physiol Regul Integr Comp Physiol. URL: https://www.ncbi.nlm.nih.gov/pubmed/12609816. In part, this increase in efficiency is due to reductions in functional mass (i.e. muscle), but mostly by decreases in ATP cost per muscle contraction.[25]Müller, MJ. / Bosy-Westphal, A. (2013): Adaptive thermogenesis with weight loss in humans. In: Obesity. URL: https://onlinelibrary.wiley.com/doi/full/10.1002/oby.20027.[26]Müller, MJ. / Enderle, J. / Bosy-Westphal, A. (2016): Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. In: Curr Obes Rep. URL:  https://www.ncbi.nlm.nih.gov/pubmed/27739007. It’s likely that such increases in exercise efficiency would diminish with increased levels of cardiorespiratory fitness, however.[27]Jones, AM. (2006): The Physiology of the World Record Holder for the Women’s Marathon. In: Int J Sport Sci Coach. URL: https://journals.sagepub.com/doi/abs/10.1260/174795406777641258.

How do our metabolisms adapt?

Adaptive thermogenesis is an extremely complex topic, so it’s no surprise that it’s still not entirely understood. As mentioned previously, the ‘why’ is predominantly due to survival. Keeping energy expenditure low to prevent body fat stores getting too low, better maintains the most important biological function: reproduction[28]Müller, MJ. / Bosy-Westphal, A. (2013): Adaptive thermogenesis with weight loss in humans. In: Obesity. URL: https://onlinelibrary.wiley.com/doi/full/10.1002/oby.20027.[29]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.[30]Rosenbaum, M., et al. (2008): Long-term persistence of adaptive thermogenesis in subjects who have maintained a reduced body weight. In: Am J Clin Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/18842775. Your body achieves this by a continuous monitoring of energy status by the hypothalamus in the brain. In ‘recognising’ low energy availability, and throughout sustained body mass losses, the regulation of AT is, amongst other factors, related to reduced endocrine signals from triiodothyronine (T3), insulin, sympathetic nervous system (SNS) activity, and reduced circulating leptin.[31]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.[32]Müller, MJ. / Geisler, C. (2016): From the past to future: from energy expenditure to energy intake to energy expenditure. In: Eur J Clin Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/27901032.

On top of the reduction in energy expenditure due to body mass losses, and those due to AT, the maintenance of weight loss is made even more difficult by an increase in appetite signalling.[33]Doucet, É. / Cameron, J. (2007): Appetite control after weight loss: what is the role of bloodborne peptides? In: Appl Physiol Nutr Metab. URL: https://www.ncbi.nlm.nih.gov/pubmed/17510692. All things considered, it’s easy to see why 80-90% of weight loss efforts are thwarted by the body’s homeostatic measures set about to defend weight loss.[34]Rosenbaum, M. / Leibel, RL. (2010): Adaptive thermogenesis in humans. In: Int J Obes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/.

As the length of your diet increases (and your body fat percentage decreases), a feedback mechanism kicks in to make you hungrier. This is related, for example, to a reduced concentration of satiety hormones (e.g. leptin, PYY. GLP-1) and an increased concentration of hunger hormones (e.g. ghrelin).

As the length of your diet increases (and your body fat percentage decreases), a feedback mechanism kicks in to make you hungrier. This is related, for example, to a reduced concentration of satiety hormones (e.g. leptin, PYY. GLP-1) and an increased concentration of hunger hormones (e.g. ghrelin). (Graphic Source: Doucet & Cameron, 2007)

Though this may make for depressing reading, these odds of success can be improved tremendously with effective nutrition and exercise interventions.

Conclusions and practical recommendations

Though often seen as independent variables, the decrease in energy intake during dieting is met with a decrease in energy expenditure. In part, this is because your body weighs less, so it requires less energy to function or to perform work/exercise. Partly, such decreases in energy expenditure also occur beyond what can be predicted by changes in body composition; this is known as adaptive thermogenesis (AKA ‘starvation mode’). This 300-400 kcal/day decrease in energy requirements associated with significant weight loss, is further compounded by increased muscular efficiency and increased appetite, making sustained weight loss the exception rather than the norm.

No need to throw in the towel: Although the human body has many defence mechanisms to slow down weight loss, with the right strategy and a little patience you can still make lasting progress. Read on and find out which tips & advice are useful.

No need to throw in the towel: Although the human body has many defence mechanisms to slow down weight loss, with the right strategy and a little patience you can still make lasting progress. Read on and find out which tips & advice are useful. (Image Source: Fotolia / zatevakhin)

With this knowledge, it’s tempting to give up on dieting altogether. The reality is, however, that one can lose weight and keep it off, it’s just a lot harder than during the initial few weeks, and requires solid nutrition and training programming, as well as a fundamental change in lifestyle. With my remaining word limit, I’ve done my best to summarize some of the more important physiological factors below.

  • Accept that fat loss will plateau. When it does, this isn’t a sign to give up; it just means that the energy deficit needs re-opening. Depending on the person’s size, genetics and extent of weight loss, we’re looking at around 200-500 fewer Calories burned per day compared to when they started. As such, further ‘nudges’ of around 250 kcal per plateau will ensure fat loss is resumed.
  • These ‘nudges’ can be in the form of either exercise of decreases in carb or fat intakes, or a combination of both. As fitness generally improves during weight loss, an improvement in exercise efficiency can be easily offset by an increase in training intensity.
  • To minimize AT-induced reductions in resting energy expenditure, strategies aimed at reducing losses in lean body mass are encouraged. These include a well-structured resistance-training programme; avoiding an excessive energy deficit by aiming for weekly reductions in body weight of roughly 0.5-1%; and by consuming protein in the region of 2-3 grams per kilogram of lean body mass per day.[35]Helms, ER., et al. (2014): A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. In: Int J Sport Nutr Exerc Metab. URL: https://www.ncbi.nlm.nih.gov/pubmed/24092765.[36]Helms, ER. / Aragon, AA. / Fitschen, PJ. (2014): Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. In: J Int Soc Sports Nutr. URL: https://jissn.biomedcentral.com/articles/10.1186/1550-2783-11-20. Higher protein diet also offer the benefit of increased satiety relative to the consumption of carbohydrate or fat.[37]Paddon-Jones, D., et al. (2008): Protein, weight management, and satiety. In: Am J Clin Nutr. URL: https://www.ncbi.nlm.nih.gov/pubmed/18469287.
  • The decrease in daily energy expenditure brought about by NEAT can be counterbalanced by integrating daily step counts into your routine. 4000-5000 steps per day is a good starting point, which can be increased up to around 10,000 per day over time.[38]Ohkawara, K., et al. (2011): How much locomotive activity is needed for an active physical activity level: analysis of total step counts. In: BMC Res Notes. URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3245484/.
  • Taking what Lyle McDonald calls a ‘full diet break’ every 12-16 weeks, whereby energy intake is restored to maintenance levels for 7-14 days, may help reverse some of the negative adaptations brought about by dieting. [39]Wing, RR. / Jeffery, RW. (2003): Prescribed ‘Breaks’ as a Means to Disrupt Weight Control Efforts. In: Obes Res. URL: https://www.ncbi.nlm.nih.gov/pubmed/12582226.[40]Jenkins, AB., et al. (1997): Carbohydrate intake and short-term regulation of leptin in humans. In: Diabetologia. URL: https://www.ncbi.nlm.nih.gov/pubmed/9084976.

Title Image Source: Fotolia / VadimGuzhva


 

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Written by Joseph Agu
Formerly a Performance Nutritionist for the English Institute of Sport (EIS) and British Athletics, Joseph is a Nutrition Consultant and Director of Elite Nutrition Coaching, specializing in nutrition for high performance and physique athletes. In addition, Joe is an Assistant Professor in Sport & Exercise Medicine at the University of Nottingham.
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