Diet alone unlikely to lead to significant weight loss

Newly published research by scientists at Oregon Health & Science University demonstrates that simply reducing caloric intake is not enough to promote significant weight loss. this appears to be due to a natural compensatory mechanism that reduces a person`s physical activity in response to a reduction in calories.The research is published in the April edition of the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology.
"in the midst of America`s obesity epidemic, physicians frequently advise their patients to reduce the number of calories they are consuming on a daily basis. This research shows that simply dieting will not likely cause substantial weight loss. Instead, diet and exercise must be combined to achieve this goal," explained Judy Cameron PH.D., a senior scientist at OHSU`s Oregon National Primate Research Center, and a professor of behavioral neuroscience and obstetrics & gynecology in the OHSU School of Medicine, as well as a professor of psychiatry at the University of Pittsburgh.
To conduct the research, Cameron and OHSU post-doctoral fellow Elinor Sullivan, PH.D., studied 18 female rhesus macaque monkeys at the Oregon National Primate Research Centre. 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% reduction in calories. For a one-month period, the monkeys` weight and activity levels were closely tracked.Activity was tracked through the use of an activity monitor worn on a collar.
"Surprisingly, there was a significant weight loss at the end of the month," explained Sullivan."However, there was a significant change in the activity levels for these monkeys. Naturally occuring levels of physical activity for the animals began to diminish soon after the reduced-calorie diet began.When caloric intake was further reduced in a second month, physical activity in the monkeys diminished even further".
A comparison group of three monkeys was fed a normal monkey diet and was traned to exercise for one hour daily on a treadmill. This comparison group did lose weight.