Exercise alone not enough to lose weight
Exercise without proper diet is not enough to lose weight. A new study says that the body adapts to increased activity levels, so that people don’t necessarily burn extra calories even if they exercise more.
“Exercise is really important for your health,” says Herman Pontzer of City University of New York. “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.”
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.
To explore this question further in the new study, Pontzer and his colleagues measured the daily energy expenditure and activity levels of more than 300 men and women over the course of a week.
In the data they collected, they saw a weak but measurable effect of physical activity on daily energy expenditure. But, further analysis showed that this pattern only held among subjects on the lower half of the physical activity spectrum. People with moderate activity levels had somewhat higher daily energy expenditures–about 200 calories higher–than the most sedentary people. But people who fell above moderate activity levels saw no effect of their extra work in terms of 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.
