Scientists found that individuals who exercise burn fewer calories for body upkeep, lowering the calorie-burning gains of exercise significantly. A particular bitter twist is that obese people and, to a lesser extent, elderly people showed the most significant drop in energy burned during rest. Sadly, some of them even gain weight when participating in an exercise regimen.

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The research team based their analysis on data from almost 2000 adults. The database included a collection of daily energy expenditure measurements made using the stable isotope method of doubly-labelled water analysis.

The scientists discovered that exercise took up 51 percent of the calories burnt at the end of the day among people with the highest BMI. However, total expenditure as a result of exercise accounted for 72 percent of calories expended during activity among those with an average BMI.

The researchers looked at how activity affects energy consumption and how these effects varied between people.

According to Professor John Speakman, co-author of the study, most people lose weight when they participate in weight-loss activity programs. Some people even lose a lot of weight, while a few individuals are unfortunate enough to actually gain weight.

The fact that some people gain weight when they participate in an exercise regimen is most likely the result of so-called compensatory mechanisms. These include eating more food because exercise increases hunger or due to lowering calory expenditure on other components, such as our resting metabolism, to make exercising less 'epensive' in terms of calory burning.

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The team was curious as to why some persons exhibit compensating mechanisms while others do not. It turns out that the degree of compensation is dominated by two factors. One factor is age, with older individuals compensating more. The other is obesity; individuals who are obese reduce their resting metabolism as they become more active. As a consequence, they save roughly half a calorie on resting for every calorie spent on activity.

This is a harsh twist for those among us who are obese. Losing weight by increasing exercise will be considerably more difficult for such people than it will be for a slimmer person, whose compensation is much lower and whose need to reduce weight is much lower.

Professor Halsley stated that national recommendations from different nations throughout the world tend to propose a 500–600 calorie deficit to reduce weight through exercise and diets. However, they do not account for the fact that the body compensates for the calories burned during exercise by burning fewer calories in the most basic of human processes.

Speakman added to this that their analysis, using data from the DLW database, explains how individuals are not all the same in the way they budget their energy use. People living with obesity may be particularly efficient at hanging onto their fat stores, making weight loss particularly challenging.

If you are interested in more details about the study, be sure to check out the paper published in the journal, Current Biology, listed below.

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