Born to Be Obese?

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"It is important not to 'blame' the obese person or imply that he/she is responsible for being obese," Kahn noted. "Having said that, reasonable, healthy caloric restriction and a safe and sustainable program of physical activity can help limit weight gain and often bring about some degree of weight loss. In addition, healthy eating and regular exercise can reduce the complications of obesity such as type 2 diabetes and cardiovascular disease."

At the same time, she added, not everyone can wear a size 4.

"There is a certain aspect of genetics that sets somebody in a certain range of possible body weights, and then how that person lives his or her life will determine whether they are at the bottom or top of the range," she explained.

Human obesity has both genetic and environmental roots. The rats used in this study, like most humans, developed obesity when fed a high-energy diet. On a normal diet, they were heavier than normal rats, but not yet obese.

"This is quite an exciting paper," said Smith, "because it links more closely to human behavior than most rodent models we have seen."

The findings also suggest a possible therapeutic approach to combating human obesity. If drugs could be designed to influence the formation of neural circuits during development and targeted to at-risk pregnancies, Smith said, "there is a good likelihood we could have successful interventions that improve the health of the mother, and which have a major impact on disease risk for the infant, during pregnancy."

A related study from Boston University researchers in the same journal found that bulking up muscle mass can lead to a general metabolic improvement in obese individuals. "Interventions designed to increase skeletal muscle mass in at-risk human populations may prove to be critical weapons in the fight against obesity and obesity-related comorbidities, including diabetes, heart disease, stroke, hypertension and cancer," an accompanying editorial stated.

More information

For more on obesity, visit the National Institute of Diabetes and Digestive and Kidney Diseases.