A new study suggests that attempting to lose weight solely by reducing the amount of calories consumed is likely to be ineffective.
The research was conducted at Oregon National Primate Research Center using adult female monkeys. Eighteen of the monkeys were fed a high fat diet for a number of years. They were then given a lower fat diet containing thirty per cent less calories for a period of one month.
During this time their weight & activity levels were carefully monitored, the latter via a device worn on a collar. The results were not what you would have expected. One of the researchers conducting the study describes what happened. “Surprisingly, there was no significant weight loss at the end of the month. 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.”
During a second month calorie intake was reduced even further to sixty per cent of the base line diet. Physical activity in the monkeys decreased even further, & there was a corresponding decrease in metabolic rate.
A second group of monkeys were fed a normal diet & trained to run on a treadmill for an hour each day for five days resulting in an increase in calories used. This group of monkeys did lose weight.
Judy Cameron - a senior scientist at Oregon Health & Science University’s national primate research center, and a professor of behavioral neuroscience and obstetrics & gynecology in the OHSU School of Medicine - was one of the two scientists who conducted the research. She said, “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 … 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.”
The researchers conclude by saying that, “…undertaking a commonly prescribed exercise program for people seeking to improve fitness is sufficient to prevent the compensatory decrease in physical activity-associated energy expenditure that slows diet-induced weight loss.”
It is hoped that the results of the research will help health professionals when giving advice to patients, and that it may also lead to interventions within the community to help combat the growing problem of childhood obesity.
