Ease of weight loss influenced by individual biology

NIH study finds varied responses to calorie restriction in obese adults.

Enrique Diaz

For the first time in a lab, researchers at the National Institutes of Health found evidence supporting the commonly held belief that people with certain physiologies lose less weight than others when limiting calories. Study results published May 11 in Diabetes.

Researchers at the Phoenix Epidemiology and Clinical Research Branch (PECRB), part of the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases, studied 12 men and women with obesity in the facility’s metabolic unit. Using a whole-room indirect calorimeter – which allows energy expenditure to be calculated based on air samples – researchers took baseline measurements of the participants’ energy expenditure in response to a day of fasting, followed by a six-week inpatient phase of 50 percent calorie reduction. After accounting for age, sex, race and baseline weight, the researchers found that the people who lost the least weight during the calorie-reduced period were those whose metabolism decreased the most during fasting. Those people have what the researchers call a “thrifty” metabolism, compared to a “spendthrift” metabolism in those who lost the most weight and whose metabolism decreased the least.

“When people who are obese decrease the amount of food they eat, metabolic responses vary greatly, with a ‘thrifty’ metabolism possibly contributing to less weight lost,” said Susanne Votruba, Ph.D., study author and PECRB clinical investigator. “While behavioral factors such as adherence to diet affect weight loss to an extent, our study suggests we should consider a larger picture that includes individual physiology – and that weight loss is one situation where being thrifty doesn't pay.”

Researchers do not know whether the biological differences are innate or develop over time. Further research is needed to determine whether individual responses to calorie reduction can be used to prevent weight gain.

“The results corroborate the idea that some people who are obese may have to work harder to lose weight due to metabolic differences,” said Martin Reinhardt, M.D., lead author and PECRB postdoctoral fellow. “But biology is not destiny. Balanced diet and regular physical activity over a long period can be very effective for weight loss.”

More than one-third of American adults are obese. Complications from obesity can include heart disease, type 2 diabetes and certain types of cancer, some of the leading causes of preventable death.

“What we’ve learned from this study may one day enable a more personalized approach to help people who are obese achieve a healthy weight,” said NIDDK Director Griffin P. Rodgers, M.D. “This study represents the latest advance in NIDDK’s ongoing efforts to increase understanding of obesity.”

The researchers will next study how lean people respond to increased caloric intake. People interested in participating in research may call 602-200-5326 or visit www.clinicaltrials.gov (Clinical Trial # NCT00687115) for information. Support for the study comes from the intramural research program of the NIDDK.

The NIDDK, a component of the NIH, conducts and supports research on diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition and obesity; and kidney, urologic and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe and disabling conditions affecting Americans. For more information about the NIDDK and its programs, see http://www.niddk.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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