New technique determines the number of fat cells remains constant in all body types

The two surveys also show increases in overweight children and teens. For children aged 2-5 years, the prevalence increased from 5 percent to 13.9 percent; for those aged 6-11 years, prevalence increased from 6.5 percent to 18.8 percent; and for those aged 12-19 years, prevalence increased from 5 percent to 17.4 percent.

In the Nature study, the team first found that there was a direct correlation between the measures of fat mass (measured from body mass index (BMI) and fat cell volume in subcutaneous fat, which represents about 80 percent of all fat, and visceral fat.

In a study of 687 adults, the researchers found that number of fat cells increases in childhood and adolescence, but levels off and remains constant in adulthood. The group looked at whether the number of fat cells changes under extreme conditions such as drastic weight loss by radical reduction in caloric intake, such as through bariatric surgery. The treatment resulted in a significant decrease in BMI and fat cell volume; however, it did not reduce the number of fat cells two years after the surgery. Similarly, significant weight gain (15-25 percent) over several months in non-obese adult men resulted in significant increase in body fat volume but no change in number. Subsequent weight loss back to baseline resulted in a decrease in fat cell volume but no change in the number of fat cells.

“If you are overweight and you lose weight, you still have the capacity to store lipids because you still have the same number of fat cells. That may be why it's so hard to keep the weight off,” Buchholz said.

Overweight and obesity result from an energy imbalance - eating too many calories and not getting enough physical activity. Body weight is the result of genes, metabolism, behavior, environment, culture and socioeconomic status. “This work may give us new ideas of how to deal with the diseases that go along with obesity,” Buchholz said.

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