Rats can be obese without overeating — all it takes is a diet high in fat, according to Lawrence B. Oscai, Margaret M. Brown and Wayne C. Miller. And, even when given the opportunity, the overweight rats don’t overeat — a finding that runs counter to previous studies. The three University of Illinois at Chicago researchers gave three groups of rats unlimited access to chow in which either 42, 50 or 60 percent of the calories came from fat.
Each of the three groups took in approximately the same number of calories as a control group eating an 11 percent fat diet, the scientists report in the current issue of GROWTH (Vol. 48). Yet all three groups of high-fat consumers weighed 32 percent more, and their carcasses were 51 percent fat, compared with 30 percent fat in the control group. “They’re eating the same amount of calories but getting fatter,” says Miller. The findings are relevant to humans: With 40 percent of the calories in the typical U.S.
diet coming from fat, getting that percentage down may be a key to weight loss, Miller says. But why would the same number of calories cause varying degrees of obesity? The Chicago group found that rats on a high-fat diet metabolize fat differently from those on a normal diet, and is now trying to detail the enzymatic changes.