The ideal weight illusion

When the goal is to lose weight, most people immediately think of reducing the number on the scale.

However, losing weight means reducing body fat - not just losing total weight. Reducing the number on the scale can reflect loss of muscle mass, bone mass, water and other tissues, in addition to body fat (Hall et al., 2012).

A successful weight loss process, especially in the medium and long term, is one that allows the majority of lean mass to be preserved, while promoting a reduction in body fat. In general, weight loss is considered metabolically healthy when more than 80% of the mass lost is fat mass (Weinheimer et al., 2010).

When strength training is not part of the process, and the diet is insufficient in protein and energy compared to the person's needs, the risk of losing muscle mass is significantly higher - and with it the risk of regaining lost fat, or even exceeding previous levels (Stokes et al., 2018).

Is BMI a good indicator?

The Body Mass Index (BMI) is a tool widely used in public health to estimate whether a person has an appropriate weight in relation to their height. However, its isolated use in an individual context is limited, as it does not distinguish between lean mass and fat mass, nor does it consider the distribution of body fat (Nuttall, 2015).

The concept of “ideal weight” is often associated with BMI, with “normal” values ranging from 18.5 to 24.9 kg/m². Although these categories are useful as a population reference, they become problematic when you want everyone to fit into these values, ignoring factors such as genetics, body structure or medical history.

Furthermore, the idea that people with a BMI within the “normal” range are automatically healthier has been questioned. Several studies show that an active lifestyle and good cardiorespiratory fitness are better predictors of health than BMI alone (Barry et al., 2014; Lee et al., 2011).

For example, people with a BMI over 30 - classified as having obesity - but with good physical function and an active lifestyle, have a lower risk of all-cause mortality than people with a so-called “normal” BMI, but with a sedentary lifestyle and unhealthy habits (Lavie et al., 2015).

It's important to emphasize that this doesn't necessarily mean excess fat has no risks, but rather that behavior has a very significant modifying impact. And in many cases, reducing fat mass through positive behavioral changes, especially when associated with a calorie-reduced diet, can be an additional protective factor.

Ideal weight... for whom?

Women, in particular, are a group especially vulnerable to the way in which the concept of “ideal weight” is culturally transmitted. From an early age, social pressure shapes the way we look at our bodies, which promotes an often unrealistic ideal - through the so-called “magazine body” - and contributes to a less healthy relationship with food.

Maybe it's time to change the paradigm from “losing weight” to “gaining health”.

In a world that constantly tries to sell us the idea that weight and health have a direct causal relationship - when this is rarely the case - it is essential to be aware of our role as professionals and citizens. This change in perspective also requires a social transformation, in which social pressure loses relevance and a more functional, sustainable and inclusive vision of all shapes and forms of the human body takes precedence.

References:

Barry, V. W., Baruth, M., Beets, M. W., Durstine, J. L., Liu, J., & Blair, S. N. (2014). Fitness vs. Fatness on All-Cause Mortality: A Meta-Analysis. Progress in Cardiovascular Diseases, 56(4), 382–390. https://doi.org/10.1016/J.PCAD.2013.09.002

Hall, K. D., Heymsfield, S. B., Kemnitz, J. W., Klein, S., Schoeller, D. A., & Speakman, J. R. (2012). Energy balance and its components: implications for body weight regulation. The American Journal of Clinical Nutrition, 95(4), 989–994. https://doi.org/10.3945/AJCN.112.036350

Lavie, C. J., De Schutter, A., & Milani, R. V. (2015). Healthy obese versus unhealthy lean: The obesity paradox. Nature Reviews Endocrinology, 11(1), 55–62. https://doi.org/10.1038/NRENDO.2014.165;SUBJMETA=2743,393,499,692,699,75;KWRD=CARDIOVASCULAR+DISEASES,OBESITY,RISK+FACTORS

Lee, D. C., Sui, X., Artero, E. G., Lee, I. M., Church, T. S., McAuley, P. A., Stanford, F. C., Kohl, H. W., & Blair, S. N. (2011). Long-term effects of changes in cardiorespiratory fitness and body mass index on all-cause and cardiovascular disease mortality in men the Aerobics Center Longitudinal Study. Circulation, 124(23), 2483–2490. https://doi.org/10.1161/CIRCULATIONAHA.111.038422/-/DC1

Nuttall, F. Q. (2015). Body mass index: Obesity, BMI, and health: A critical review. Nutrition Today, 50(3), 117–128. https://doi.org/10.1097/NT.0000000000000092

Stokes, T., Hector, A. J., Morton, R. W., McGlory, C., & Phillips, S. M. (2018). Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy with resistance exercise training. Nutrients, 10(2). https://doi.org/10.3390/NU10020180,

Weinheimer, E. M., Sands, L. P., & Campbellnure, W. W. (2010). A systematic review of the separate and combined effects of energy restriction and exercise on fat-free mass in middle-aged and older adults: implications for sarcopenic obesity. Nutrition Reviews, 68(7), 375–388. https://doi.org/10.1111/J.1753-4887.2010.00298.X