Dietary Fat Intake – Does it Affect Weight?

The following advice has become a mantra engrained in our society’s battle of the bulge: “If you want to lose weight and improve your health, eat a low fat diet”. And for years I bought into this during the carb-frenzy fat-free 1990s. But then I entered graduate school and started reading the research (and I was just plain hungry all the time).  A low fat did work for many people who were obese or overweight because cutting fat meant they cut calories and therefore dropped weight. And for those with cardiovascular disease risk factors, slashing the fat in their diet automatically meant a decrease in bad fats so their cholesterol levels improved. It shouldn’t come as a surprise that taking someone off fried foods and partially hydrogenated snack foods will improve their cholesterol levels.

But do we need low fat for weight loss?  According to my good friend and well respected scientist, Jose Antonio, the answer is no. And, a recently published study in the American Journal of Clinical Nutrition backs this viewpoint. In this particular study, scientists analyzed data from 89,432 men and women from 6 cohorts of the European Prospective Investigation into Cancer and Nutrition (EPIC) study. They analyzed data between baseline fat intake (amount and type from total fat, polyunsaturated, monounsaturated and saturated fats) from food frequency questionnaires and annual weight change and, after adjusting for anthropometric data, lifestyle and dietary factors, they found no significant relationship between dietary fat intake and weight gain. The authors concluded that “these findings do not support the use of low-fat diets to prevent weight gain.”

This study did have some drawbacks. After all, food frequency questionnaires are limited, they only analyzed fat intake at one point in time and not over time and they didn’t examine data on trans fat intake. After all, this wasn’t a clinical trial in rats (the most compliant subjects ever) where they could manipulate variables and see if people grow or shrink in size.

These results are different than those from some other studies but overall, the research is equivocal on the subject of fat and weight. A review of 9 studies examining fat and weight change found 3 studies found a positive association between type of fat and weight change, 3 found no association and the last 3 reported negative association.

What’s the bottom line? Eat your fat, but choose healthy fats (fish fat, nuts, seeds, oils) and avoid partially hydrogenated oil (man made trans fats) and if you have heart disease risk factors, watch your saturated fat consumption too.