New York, Jan 29 (IANS): Exercising is important in order to burn calories and stay fit. But a recent study says that exercise alone is not always enough to shed weight as our bodies adapt to higher activity levels and do not burn extra calories even if we exercise more.

According to the researchers, 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 makes unhealthy but too much makes big adjustments in order to adapt.

"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,” said researcher Herman Pontzer from City University of New York in the Cell Press journal Current Biology.

“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," Pontzer added.

People who start exercise programmes 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, researchers carried out a study to measure the daily energy expenditure and activity levels of more than 300 men and women over the course of a week.

The research showed 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.

The results suggest, it's time to rethink the effect of physical activity on daily energy expenditure. They are also a reminder of the importance of diet and exercise in supporting weight loss goals, the researchers said.