Exercise by itself isn’t always enough to take off the weight. Now, evidence reported in the Cell Press journal Current Biology on January 28 helps to explain why that is: our bodies adapt to higher activity levels so that people don’t necessarily burn extra calories even if they exercise more. The results suggest it’s time to rethink the effect of physical activity on daily energy expenditure, the researchers say. They are also a reminder of the importance of diet and exercise in supporting weight loss goals.
Exercise is really important for your health. There is tons of evidence that exercise is important for keeping our bodies and minds healthy, and this study does nothing to change that message. What this study 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.
People who start exercise programs to lose weight often see a decline in weight loss (or even a reversal) after a few months. Large comparative studies have also shown that people with very active lifestyles have similar daily energy expenditure to people in more sedentary populations.
Pontzer, from the City University of New York, says this really hit home for him when he was working among the Hadza, a population of traditional hunter-gatherers in northern Tanzania. The Hadza are incredibly active, walking long distances each day and doing a lot of hard physical work as part of their everyday life. Despite these high activity levels, Pontzer and colleagues found that they had similar daily energy expenditures to people living more sedentary, modernized lifestyles in the United States and Europe. That was a real surprise, and it got them thinking about the link between activity and energy expenditure. After collecting data on more than 300 men and women this study revealed that:
- People with a moderate activity level had somewhat higher energy expenditure (about 200 calories more) than most sedentary people.
- Those who had above-normal activity levels saw no effect in terms of extra energy expenditure! “The most physically active people expended the same amount of calories each day as people who were only moderately active,” Pontzer says.
The researchers say it’s time to stop assuming that more physical activity always means more calories. There might be a “sweet spot” for physical activity–too little and we’re unhealthy, but too much and the body makes big adjustments in order to adapt.
Losing fat while gaining muscle:
Scientists close in on ‘holy grail’ of diet and exercise
Researchers at McMaster University have uncovered significant new evidence in the quest for the elusive goal of gaining muscle and losing fat, an oft-debated problem for those trying to manage their weight, control their calories and balance their protein consumption. Scientists have found that it is possible to achieve both, and quickly, but it isn’t easy.
For the study, 40 young men underwent a month of hard exercise while cutting dietary energy they would normally require by 40 percent of what they would normally require. The researchers divided their subjects into two groups. Both groups went on a low-calorie diet, one with higher levels of protein than the other. The higher-protein group experienced muscle gains — about 2.5 pounds — despite consuming insufficient energy, while the lower protein group did not add muscle.
The lower-protein group at least had the consolation of not losing muscle, which is a predictable outcome of cutting calories and not working out, say researchers. “Exercise, particularly lifting weights, provides a signal for muscle to be retained even when you’re in a big calorie deficit,” said researchers!