The percentage of calories that a person got from fat, as opposed to protein or carbohydrates, had nothing to do with how much weight they gained in the coming years, the research team found.
The kinds of fat they ate didn't matter either, Dr. Nita Forouhi of the Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK and her colleagues found.
The findings, Forouhi noted in an email to Reuters Health, show that "it is more important to aim for a healthy lifestyle including a balanced healthy diet and regular physical activity, than to focus on fat intake alone as a factor for weight gain."
The role of dietary fat content in obesity and weight gain is still controversial, Forouhi and her team note. To investigate, they looked at data on nearly 90,000 men and women from six different countries participating in the European Prospective Investigation into Cancer and Nutrition Study. Participants were followed for up to 10 years.
Average fat intake ranged from 31.5 percent to 36.5 percent of total calories. On average, people gained about a quarter of a pound every year. But analyses that accounted for several factors found no relationship between how much weight people gained and how much fat they ate, or their intake of polyunsaturated fats versus saturated fats.
The findings shouldn't be seen as showing that people can eat as much fat as they want, Forouhi said. "That would be absurd, given so much evidence that already exists on the potential harms of diets high in saturated or trans-fats for heart health for instance," the researcher said.
In the US, she added, dietary recommendations state that people should maintain a fat intake that is 20 percent to 35 percent of total calories, and eat "healthy" fats from fish, nuts, and vegetable oils instead of "unhealthy" saturated and trans fats.
She added: "The healthiest way to avoid weight gain is to make sure that, when appropriate, total calorie intake is limited by reducing one's intake of added sugars, fats, and alcohol, which all provide calories but few or no essential nutrients, to watch portion sizes of food (so food portions consumed do not increase in size over time), and at the same time take regular physical activity."
SOURCE: American Journal of Clinical Nutrition, December 200