Times of India
15 April 2010
Want to lose weight? But only dieting will not do
A study by the scientists at Oregon Health and Science University in US showed that simply dieting is not enough to promote significant weight loss due to a natural compensatory mechanism that reduces a person’s physical activity in response to a reduction in calories.
The researchers said that for substantial weight loss diet and exercise must be combined.
In the research, published in the ‘American Journal of Physiology’, an international team led by Judy Cameron studied 18 female rhesus macaque monkeys at the Oregon National Primate Research Center.
The monkeys were placed on a high–fat diet for several years. They were then returned to a lower–fat diet (standard monkey food) with a 30 percent reduction in calories.
The researchers closely tracked the monkeys’ weight and activity levels for a onemonth period. The scientists used an activity monitor worn on a collar.
“Surprisingly, there was no significant weight loss at the end of the month,” the team said. “However, there was a significant change in the activity levels for these monkeys.
“Naturally occurring levels of physical activity for the animals began to diminish soon after the reduced–calorie diet began”.
Cameron said: “When caloric intake was further reduced in a second month, physical activity in the monkeys seemed to diminish even further.”
The team then fed another group consisting of three monkeys a normal monkey diet and trained them to exercise for one hour daily on a treadmill. they found that this comparison group did lose weight.
“This study demonstrates that there is a natural body mechanism which conserves energy in response to a reduction in calories.
“Food is not always plentiful for humans and animals and the body seems to have developed a strategy for responding to these fluctuations,” Cameron added.
“These findings will assist medical professionals in advising their patients.
“It may also impact the development of community interventions to battle the childhood obesity epidemic and lead to programmes that emphasise both diet and exercise.”