Burning Calories From High-Fat Meals: How the Body Reacts
Many of us know from experience that even the occasional "high-fat" binge (during the holidays or special events) can have a lasting impression on your waistline. The exact biological mechanism for it was explained recently at a conference on reducing dietary fat, covered by Jane Brody of The New York Times.
Dr. John Blundell, a psychobiologist from the University of Leeds (England), has done extensive research in the field of fat consumption. He has found some surprising information about the role that fat plays in appetite suppression: "High-fat foods disturb appetite control while people are in contact with food and afterward -- for the rest of the day and even the next day." Even more significant is the effect these high-fat binges may have on weight control, in the form of calorie burning.
A meal high in fat content will have more calories than a similar-sized meal high in protein or carbohydrates, as fat grams have nine calories per gram compared to four each for protein and carbohydrates. When eating the same amount of food until satiation or feeling "full," the meal high in fat will have included significantly more calories. In fact, Dr. Blundell's studies have shown a nearly two-to-one calorie ratio between high-fat and high-carbohydrate meals, or 1350 to 680 calories in one meal consumed.
The increased caloric content is obviously an important factor, but Dr. Blundell also discussed the "fat paradox" of satiation. Dieters often complain that low-fat meals don't "fill them up" as well; in fact, when you consume a high-fat meal, you do feel full sooner, but not soon enough that you haven't ingested a significantly higher number of calories.
Oxidation, or burning, of fat calories is even more significant to weight gain than caloric intake. When the body receives only occasional meals high in fat calories, it stores those fat calories immediately. The body only begins to oxidize fat calories aggressively when it receives a steady, rich supply of those calories: according to Dr. Blundell, it takes three to seven days of high-fat eating to increase fat oxidation.
This is particularly significant for the high-fat "binger", one who only rarely consumes a high-fat meal. Carbohydrate calories are burned off quickly: the body can only store about 3500 carbohydrate calories in the liver and muscles, oxidizing the rest as heat energy. But the body holds tightly to fat calories. Besides not being able to burn those fat calories through exercise, Dr. Blundell found that, after consuming a high-fat meal, there seems to be no tendency to eat less in subsequent meals; the fat calories remain in storage. And, as many of us have observed and Dr. Blundell has studied, "There is no limit to how much fat we can store," resulting, inevitably, in weight gain.
The conference on reducing dietary fat was co-sponsored by the American Health Foundation, the National Cancer Institute, the American Heart Association and the American Society of Preventive Cardiology. Dr. Blundell notes that his studies have shown that healthy and even underweight individuals may partake of a high-fat diet, and that there is no "biological imperative" that a high-fat diet leads to obesity. However, he noted, his studies showed that older individuals had a higher tendency to be overweight.
HeartInfo Editorial Comment:
There are many advantages to eating a lower fat diet, only one of which is related to having a lower cholesterol level. Low-fat diets decrease risk of heart disease, certain cancers, and certain intestinal problems. They are also less likely to lead to obesity, as outlined in this elegant study. We should all look carefully at our diets and cut out fat (especially saturated fat) wherever possible.
The New York Times, December 18, 1996