Eating can be a key factor
For a long time, a sedentary lifestyle in industrialized countries has been considered the main cause of high obesity rates. However, a new study published in the journal PNAS challenged this assumption.
Using data from more than 4,000 adults in 34 different population groups, the research team found that the daily energy expenditure of US office workers is almost equivalent to that of farmers in Siberia, gardeners in Bolivia or hunters in Tanzania.
After adjusting to the body size, we found that the difference in energy expenditure between regions was very small, said Dr. Amanda McGrosky, Associate Professor of Biology at Elon University (USA). This suggests that diet, not exercise, is the main factor causing obesity.
One reason may be that in rich countries, the immune system consumes less energy to fight infections, leading to lower basal expenditure.
The body has limitations in energy consumption
The above results reinforce the restricted daily energy expenditure model developed by researchers Herman Pontzer and Amy Luke. This model suggests that humans have evolved to burn the maximum amount of calories per day, regardless of physical activity.
I was surprised to learn that a person who walks 15km a day consumes the same number of calories as a person sitting at a desk, if they are the same size, says Dr McGrosky.
Research also shows that heavy athletes can burn a lot of calories in the short term, but the average consumption will gradually decrease because the body allocates energy to other functions such as immunity or growth.
Not all scientists agree with this hypothesis. Some still believe that the combination of exercise and diet is the deciding factor.
Easy access to calories is a "guide"
According to Dr. McGrosky, the high rate of body fat in industrialized countries is mainly due to access to high-calorie foods, especially ultra-processed foods.
Exercise is important for your health, but its not an effective tool for weight loss if you dont control your diet, says Dr. Jeff Horowitz, Professor of Exercise Science and Director of the Chemical Metabolism lab at the University of Michigan.
He gave an example: Eating a Big Mac with French fries and Coca-Cola only takes 10 minutes, but to burn those calories with running, you need about 19 km.
Nutritionists are still debating whether two foods have the same calorie content but different quality that have different effects on body fat. However, most people agree that eating more calories than you consume will definitely lead to weight gain.
Maintaining exercise is still necessary for overall health, but a balanced diet can play a more important role in preventing obesity.
