NUTRITION MISCONCEPTIONS II –Low-Calorie Diets

Are low-calorie diets an effective fat-loss strategy? Maybe not.

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With so many fad diets around these days, it’s no wonder people are confused about good nutrition. No doubt, weight loss is a beast of a task to tackle. You take weight off, it comes right back, you take it off again. Our bodies are genius and know exactly what

they need and how to get it. The body is highly adaptable and a relentless survivor. So, when you start to mess with the very mechanisms (ie: energy storage; aka fat) to keep it alive, a cascade of events, designed to preserve the hard earned energy savings account, is triggered. What are some of the mechanisms? Read on to learn more:

Ever heard the term adaptive thermogenesis? If you have, I bet you never gave it a second thought. Adaptive thermogenesis is defined as the “regulated production of heat in response to environmental changes in temperature and diet, resulting in metabolic inefficiency”.(1)

When an individual reduces calorie intake and weight loss results, the body's adaptive process is to prioritize storage, and lower energy output, hence decreasing metabolism. Since lean muscle mass requires more energy than fat, it’s not an immediate priority for the body. The metabolic rate, or metabolic efficiency, is lowered as a result, and decreases the body’s capacity or willingness to burn fat. Adaptive thermogenesis creates the ideal situation for weight regain in both lean and obese individuals who are attempting to sustain reduced body weight.

Eventually, adaptive thermogenesis rebounds lost weight, in the form of fat mass, which makes the body look bigger and increases cardiometabolic risks. Consequently, not only does eating result in excess fat, but eat too little food can also result in loss of lean muscle mass and excess fat.(2)

The process of weight loss and regain is also referred to as weight cycling, or "yo-yo" dieting, which may have adverse health effects on skeletal, cardiovascular, and renal (kidney) systems. Due to the higher risk of losing fat-free mass, including bone mass, weight cycling may increase risk of bone fracture and relative sarcopenic obesity, in which low skeletal muscle mass is coupled with high levels of adiposity. Sarcopenia is associated with falls, functional decline, frailty, and mortality.

As shown in the figure below, weight cycling can also lead to repeated overshoot of some cardiovascular and renal risk factors during the weight gain phase. These fluctuations may put additional stress on the cardiovascular and renal systems, which may contribute to overall increases in morbidity and mortality. (2)

It is important to note dieting and weight cycling are not limited to those who are obese or overweight; this can occur with individuals in a normal range of healthy body weight who attempt to lose weight. In fact, there is emerging evidence showing that cardiovascular risk factors of dieting and weight cycling are more readily seen in people of normal weight rather than in those who are overweight or obese. (2)

In addition, there is a possible relationship between energy deficits and disordered eating. Due to the mechanism of adaptive thermogenesis, people trying to lose weight will return to their original weight, but with higher fat mass. In order to maintain a desired weight and/or body composition, further reduced energy intake is required. Eventually, this pattern may lead to an eating disorder. (4)

If low-calorie diets cannot help with losing fat mass, then what kind of diet can? We will explain more in the next blog. See you then!

Content contributed by Yuyi (Amber) Chen currently a bio-major student at Emory University. Originally from Hangzhou, China, Yuyi has been studying in the US for 8 years. Yuyi is interested in nutrition and hopes to use her knowledge to help people maintain a healthy lifestyle.

Reference

1. Joosen, A. M., & Westerterp, K. R. (2006). Energy expenditure during overfeeding. Nutrition & Metabolism, 3, 25. https://doi.org/10.1186/1743-7075-3-25

2. Montani, J.-P., Schutz, Y., & Dulloo, A. G. (2015). Dieting and weight cycling as risk factors for cardiometabolic diseases: Who is really at risk? Obesity Reviews: An Official Journal of the International Association for the Study of Obesity, 16 Suppl 1, 7–18. https://doi.org/10.1111/obr.12251

3. Svetkey, L. P., Stevens, V. J., Brantley, P. J., Appel, L. J., Hollis, J. F., Loria, C. M., Vollmer, W. M., Gullion, C. M., Funk, K., Smith, P., Samuel-Hodge, C., Myers, V., Lien, L. F., Laferriere, D., Kennedy, B., Jerome, G. J., Heinith, F., Harsha, D. W., Evans, P., … Weight Loss Maintenance Collaborative Research Group, for the. (2008). Comparison of Strategies for Sustaining Weight Loss: The Weight Loss Maintenance Randomized Controlled Trial. JAMA, 299(10), 1139–1148. https://doi.org/10.1001/jama.299.10.1139

4. Benardot D & Thompson W. ACSM Health and Fitness Journal 1999; 3(4): 14-18