You’ve started an exercise regime with the aim of shedding a few pounds. During the first few weeks, things are great and you lose some weight. Then, after a few weeks or when putting in some extra sessions, the weight loss stops (or even comes back on). The new study indicates there is a reasonable explanation for this.
In essence, the research shows that after working out for a period of time putting more hours in the gym does not necessarily burn extra calories. This is because a point is reached where burning more calories becomes increasingly difficult. The new research counters new obesity prevention advice issued by the U.K. government.
From a physiological perspective, the research shows there is a point where exercise helps those who are unhealthy to lose weight and improve fitness. However, after a threshold is passed (described as “too much exercise”) this triggers the body to undergo an adjustment to adapt to the effort being expelled; this leads to the body constraining total energy expenditure. That is, the body starts to do all it can not to burn calories.
The research is not quite as counterfactual as it appears. It has long been known, for example, that active populations (like hunter-gatherers in Africa) do not have particularly high total energy expenditure.
The finding was based on a study of 332 from Africa and North America. The subjects were studied over the course of a week, and their eating habits and exercise regimens correlated with measurements of the total calories burned.
Speaking with The Guardian, one of the lead researchers, Professor Herman Pontzer of City University in New York, explains: “Exercise is really important for your health. That’s the first thing I mention to anyone asking about the implications of this work for exercise. There is tons of evidence that exercise is important for keeping our bodies and minds healthy, and this work does nothing to change that message. What our work adds is that we also need to focus on diet, particularly when it comes to managing our weight and preventing or reversing unhealthy weight gain.”
In order to help with weight loss, the World Health Organization advises that only diet and exercise together is effective.
The new research is published in the journal Current Biology. The paper is titled “Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans.”
