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14 Oct

The debate surrounding the efficiency and sustainability of long dieting periods with smaller caloric deficits versus shorter dieting periods with larger deficits has garnered much attention in the bodybuilding and fitness communities. Central to this discussion is the phenomenon of metabolic adaptation, a complex set of physiological changes where the body reduces its metabolic rate to conserve energy. One key factor in metabolic adaptation is the role of the thyroid gland, specifically the production of thyroid hormones T3 and T4, which are crucial for regulating metabolism. This article will delve into both dieting approaches and their effects on metabolism, thyroid function and muscle mass providing insight into which may be the optimal strategy for body composition.

Shorter Dieting Periods with Larger Deficits

While shorter dieting periods with larger caloric deficits offer the appeal of quick results, the metabolic implications can be more complex. A significant caloric deficit sends a signal to the body, via the pituitary gland to the thyroid, to conserve energy, activating survival mechanisms that reduce metabolic rate, sometimes referred to as “starvation mode.” This reduction in metabolic rate can make it increasingly difficult to continue losing weight and may lead to a plateau with further reduction is calories, increasing the rate of muscle loss.

Even after the dieting period is over, the body may continue to operate at this reduced metabolic rate for longer periods of time, another drawback of Metabolic Adaptation. This adaptation can make weight maintenance and future weight loss efforts more challenging. According to a study published in the “International Journal of Obesity,” participants of “The Biggest Loser” competition experienced a significant and persistent drop in their resting metabolic rate, even six years after the end of the competition [1].

For those in long dieting phases like Contest Prep, it’s crucial to be aware of this metabolic slowdown. The metabolic adaptations that occur due to larger caloric deficits can make it challenging to achieve the desired physique within the competition timeline. Therefore, if opting for this approach, it’s essential to have contingency plans in place to counterbalance the potential negative metabolic effects.

Long Dieting Periods with Smaller Deficits

Opting for longer dieting periods with smaller caloric deficits offers some advantages, primarily in the form of less drastic metabolic adaptations. While still inducing a caloric deficit sufficient for weight loss, smaller deficits are less likely to trigger the severe hormonal responses that larger deficits can. This makes it easier to maintain a more stable metabolic rate over the long term.

A 2009 study found that moderate caloric restriction did not produce the same extent of metabolic slowdown as experienced in more extreme caloric restriction [2]. Additionally, smaller deficits over an extended period offer the advantage of muscle preservation. According to a review in the International Journal of Sport Nutrition and Exercise Metabolism, adequate protein intake alongside a moderate caloric deficit can optimize muscle protein synthesis, aiding in the retention of lean muscle mass during weight loss [3].

For those in the Off-season or focusing on Lifestyle changes, this approach provides a more sustainable pathway for long-term metabolic health and easier dieting phase, to include preps. It allows for greater flexibility in dietary choices, making it easier to adhere to in the long run. However, it’s important to note that the slower rate of weight loss might not be suitable for those on a tight Contest Prep schedule.

In the realm of long dieting periods with smaller caloric deficits, it’s crucial to discuss not just metabolic implications but also psychological factors. Research indicates that more extended, moderate dieting phases can be psychologically easier to adhere to, increasing long-term success [4]. Moreover, the flexibility in caloric intake means athletes are less likely to feel deprived or restricted, making it more likely for them to maintain good nutritional habits.

Another important note is the potential for more effective nutrient partitioning. When the body is not in an extreme caloric deficit, it may more effectively allocate nutrients toward muscle repair and growth, offering a dual benefit of fat loss and muscle retention [5].

From an endocrine standpoint, smaller deficits over longer periods are less likely to elicit stress responses, such as increased cortisol levels, which can further sabotage muscle retention and metabolic rate [6].

The Endocrine Impact of Larger Caloric Deficits

A critical consideration in the context of larger caloric deficits and metabolism is the influence on the endocrine system, specifically the interaction between the pituitary and thyroid glands. When confronted with a significant caloric deficit, the pituitary gland often decreases the secretion of Thyroid-Stimulating Hormone (TSH). This reduction can result in suppressed production of thyroid hormones T3 and T4, which are vital for maintaining metabolic rate [7].

A study in the “American Journal of Physiology” illustrates that even short-term caloric restriction can significantly alter T3 levels, indicating immediate metabolic adaptations [8]. Another study published in the “Journal of Clinical Endocrinology & Metabolism” found that low-calorie diets led to a substantial decrease in T3 levels, impacting metabolic rate [9]. These changes can be more severe with larger deficits than with smaller deficits sustained over a longer period. The larger caloric deficits can lead to a more significant reduction in thyroid hormones T3 and T4, which in turn affects metabolic rate. This is often observed as part of the body’s adaptive mechanisms to conserve energy during periods of significant caloric restriction [7[8][9].

Metabolic Considerations

Both dieting strategies have unique metabolic consequences. Longer periods with smaller deficits tend to have a less pronounced effect on the metabolic rate and high muscle retention, while shorter periods with larger deficits can lead to a more rapid metabolic slowdown, and less muscle retention. The latter may make subsequent Contest Preps more challenging, and time between prep longer due to the lingering effect of Metabolic Adaption resulting from an excessive deficit.


When choosing between long dieting periods with smaller deficits and shorter periods with larger deficits, consider not just the speed of weight loss but also the long-term metabolic consequences and the ability to preserve muscle mass. Both approaches have pros and cons, and the choice should be tailored to individual metabolic responses, the timeframe available, and the goals set for stage appearance or future preps.


[1] Fothergill, E., Guo, J., & Howard, L. (2016). Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. International Journal of Obesity.

[2] Redman LM, Heilbronn LK, Martin CK, de Jonge L, Williamson DA, Delany JP, Ravussin E; Pennington CALERIE Team. Metabolic and behavioral compensations in response to caloric restriction: implications for the maintenance of weight loss. PLoS One. 2009;4(2)

[3] Helms, E. R., Zinn, C., Rowlands, D. S., & Brown, S. R. (2014). A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Nutrition & Metabolism.

[4] Byrne S, McLean N. Elite athletes: effects of the pressure to be thin. J Sci Med Sport. 2002 Jun;5(2):80-94.

[5] Aragon, A. A., & Schoenfeld, B. J. (2013). Nutrient timing revisited: is there a post-exercise anabolic window? Journal of the International Society of Sports Nutrition.

[6] Hill, E. E., Zack, E., Battaglini, C., Viru, M., Viru, A., & Hackney, A. C. (2008). Exercise and circulating cortisol levels: the intensity threshold effect. Journal of Endocrinological Investigation.

[7] Samuels, M.H. (2008). Effects of variations in physiological cortisol levels on thyrotropin secretion in subjects with adrenal insufficiency: a clinical research center study. Journal of Clinical Endocrinology & Metabolism.

[8] Klieverik, L.P., Coomans, C.P., Endert, E., Sauerwein, H.P., Havekes, L.M., Voshol, P.J., Rensen, P.C.N., Romijn, J.A., & Kalsbeek, A. (2009). Thyroid Hormone Effects on Whole-Body Energy Homeostasis and Tissue-Specific Fatty Acid Uptake In Vivo. American Journal of Physiology.

[9] Spaulding, S.W., Chopra, I.J., Sherwin, R.S., & Lyall, S.S. (1976). Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man. Journal of Clinical Endocrinology & Metabolism.