Surprisingly, people with a low BMI do less physical activity than others… But they eat smaller quantities.
- Waist circumference is another indicator for diagnosing overweight or obesity.
- It is considered too high from 80 cm for a woman and 94 cm for a man.
If sport is excellent for health in general, it does not always allow you to lose weight or stay thin… Indeed, according to a study published in the journal Cell Metabolism, people with a lower body mass index (BMI) do 23% less physical activity compared to people with a higher BMI. But they ate in smaller amounts, 12% fewer calories than those with a higher BMI.
Overweight from 25
The BMI is an indicator which makes it possible to estimate the corpulence of an individual. To calculate it, simply divide the weight in kilograms by the height in centimeters squared. The result of this operation gives a figure which determines in which category the person is located: undernutrition (below 16.5), thinness (from 16.5 to 18.5), normal corpulence (from 18.5 to 25) , overweight (from 25 to 30), moderate obesity (from 30 to 35), severe obesity (from 35 to 40), morbid or massive obesity (over 40).
The metabolism
“We expected these people to be really active and to have high activity metabolic rates corresponding to high food intakes.explains John Speakman, one of the authors of the study. It turns out that something quite different is going on. They had lower food intake and activity, as well as surprisingly higher than expected resting metabolic rates linked to elevated thyroid hormone levels“.
Thyroid hormones
The thyroid is a small gland located in the neck that secretes thyroid hormones. These control the speed of chemical functions in the body, i.e. basal metabolism, and affect many vital body functions, such as heart rate or the rate at which calories are burned. .
Normally, it is when a person exercises regularly that he gains muscle mass. This has an impact on his metabolism which works in a better way. Thus, even at rest, the muscle consumes more energy than the fat mass and the metabolism therefore spends more energy and burns calories.
12% fewer calories
According to scientists, if people stay thin without doing sports, it is because they eat less. To reach this conclusion, the researchers followed two types of people: 173 participants had a normal BMI and 150 a BMI below 18.5. For two weeks, they recorded their food intake and their physical exercise sessions. Thus, they observed that those with a BMI of less than 18.5 consumed 12% less food and were 23% less active compared to the others.
Energetic cost
“Although these very skinny people had low levels of activity, their markers of heart health, including cholesterol and blood pressure, were very good., explains Sumei Hu, one of the authors of the study. Indeed, scientists have observed that people with a BMI of less than 18.5 have high resting energy expenditure and thyroid activity.
Sport remains essential
In the future, scientists intend to continue their research in order to better understand the reasons for this phenomenon… And thus, perhaps, be able to find new solutions to help overweight people lose weight.
But the results of this study are not an incentive not to play sports, quite the contrary. To be healthy,World Health Organization (WHO) recommends that adults aged 18 to 64 do at least 150 to 300 minutes of moderate-intensity sport or 75 to 150 minutes of vigorous-intensity sport per week.