Author: Siddharth Lall, Nutrition consultant at SQUATS,INFS alumni
- Any caloric restricted diet leads to metabolic changes that favor conservation of body weight and prevention of further weight loss.
- Crash dieting is accompanied by alterations in the hormones that regulate appetite, hunger and satiety such as leptin, thyroid, ghrelin, sex hormones etc.
- Crash diets often lead to a significant reduction in TDEE, primarily due to the rapid drop in BMR, which is the largest contributing factor to the TDEE.
- Another contributing factor to the metabolic adaptations is mitochondrial efficiency that further serves to reduce the TDEE.
- Metabolic damage is a just myth and crash diet or any calorie-restricted diet causes a temporary metabolic slowdown. However, this temporary slowdown of metabolism is enough to put you on a risk of weight regain
Whether it’s to shed those extra kilograms right before your friend’s marriage or to fit into that dress before your anniversary, many turns to crash diets to get the job done. GM Diet, miracle diet, water diet, detox diet, Slim-Fast – the list of crash diets is endless and there is always another new amazing weight loss plan which seems to good to be true. Unfortunately, there’s no shortcut when it comes to fat loss.
Crash Diet-induced weight loss out-turns several physiological changes and scores of homeostatic metabolic adaptations in the body, which is followed by metabolism slowdown. It’s important to note that these metabolic adaptations to crash-diet continue even after the diet and if followed by striking increase in energy intake, it leads to rapid accumulation of fat mass as well consequently. It is common for an individual to “overshoot” their homeostatic body fat percentage in this case. Thus, a crash-diet traps a short-term weight loss followed by an acute weight regain. Such repeated cycle of weight loss and regain results in long-term obesity
This article will give you a brief idea about these metabolic adaptations and hormonal changes that actually contribute to the metabolic slowdown.
Hormonal response to crash diet
Hormones play significant roles in the regulation of body composition, energy intake, and energy expenditure. When you “starve” on these kind of crash diets, the endocrine system is the first one to be affected simply because the body doesn’t have sufficient energy to produce/maintain the level of these hormones. Some of the hormones that are affected are:
1)Thyroid: The hormones of the thyroid gland, are known to play an important and direct role in regulating metabolic rate. Increases thyroid hormones are associated with an increase in the metabolic rate, whereas lowered thyroid levels result in decreased thermogenesis and overall metabolic rate .
2) Leptin: Leptin, is secreted by adipocytes(fat cells) and functions as an indicator of energy availability, satiety signals and controls energy expenditure.
3) Insulin: Insulin, is another crucial hormone that is considered as an “adiposity signal”. Likewise leptin, insulin levels also signals energy availability and are associated with an anorexigenic effect.
4) Ghrelin: Ghrelin, conversely to leptin and insulin, is an orexigenic hormone which is responsible to increase appetite and food intake.
5) Testosterone: Testosterone, a hormone that plays role in increasing muscle protein synthesis and muscle mass may also play a role in regulating adiposity.
Adaptations in Thermogenesis
In any hypo-caloric diet, TDEE (Total daily energy expenditure) has been consistently shown to decrease and get suppressed. Weight loss done in absence of sufficient protein results in a loss of metabolically active muscle tissues, and therefore decreases BMR. Muscle tissues are metabolically active and burn calories at rest, therefore loss in muscle tissues reduces the amount of calories burnt at rest thus reduces the BMR.
Continued suppression of TDEE may contribute to weight regain in the post- diet period. Adaptive thermogenesis and decreased energy expenditure continues to exist even after diet period is over. These adaptations serve to minimize the energy deficit, inhibit further weight loss and promote weight regain.
Mitochondrial & Metabolic efficiency
Energy restriction has been shown to increase metabolic and mitochondrial efficiency, which burns fewer calories from ingested food and lower the rate of thermogenesis.
These changes serve to decrease the energy deficit in hypo-caloric conditions, making weight reduction and further weight maintenance more challenging
Myth of Metabolic Damage
We have often heard this word “Metabolic damage “ given to the above metabolic adaptations which takes place while crash dieting. Metabolic Damage is a word, which may seem like a permanent loss of metabolism but that is not the truth. The above adaptations are not always long term but a temporary slow down. They can definitely be recovered or retained by taking the right measures and precautions while dieting like shorter expanse of deficit, optimum protein intake, resistance training and planned diet breaks which we will discuss in the upcoming articles of this series.
A crash diet involves eating at severe caloric deficit for maximum possible. Simply put, these types of diets are doomed to failure and are not the best strategy to lose fat, as they aren’t sustainable. Any calorie restricted diet leads to certain temporary physiological adaptations as a result of your body’s attempt to maintain energy balance and prevent starvation. The degrees of these adaptations are related to the extent of deficit maintained. Since, crash diet encourages intake of extremely low calories, the metabolic adaptations kick in faster that also adversely affect the endocrine system.
In nutshell, you can lose those 5-6 Kg right now with same insane, fad diets, but if you do, you’ll just gain that weight back, and your metabolism will be worse for it, and things will be even harder for you next time. Sometimes the shortest path to your ultimate goal is not the best way. If you really want to lose weight and keep it off, you need to forget about short-term cosmetic goals for long-term metabolic health and sustainable fat loss.
Excerpt from a chapter in INFS health series for slow metabolism – which will be released very soon.
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