When it comes to lowfat diets, many questions can be asked. What comprises a lowfat diet? Is one man’s “lowfat” diet another man’s “moderate-fat” diet? And if fats are so important, why do some people feel better when they go on lowfat diets?
Sixty years ago, recommendations for the amount of fat allowed in therapeutic diets could range from the very lowfat (high-protein) diet used to treat nephrosis, a type of kidney disease, (18 percent of the energy as fat) to the very high-fat diet used to treat epilepsy in children (88 percent of the energy as fat). In between was the “lowfat” diet used for treatment of obesity (32 percent of energy as fat) and the relatively high-fat therapeutic diets used for convalescence from serious illness (49-56 percent of energy as fat).1
By analyzing menus from turn-of-the-century cookbooks, we can estimate that the fat content of the diets at that time was about 35-40 percent of energy as fat. Fats contain about twice as many calories per gram as protein or carbohydrate foods. In a diet of 2500 calories, 35 percent of calories as fat translates to 97 grams of fat (slightly less than 1/2 cup) per day, as added fat or distributed in the foods. Pictures of the general populace at the time do not show large numbers of obese individuals, and in fact they showed mostly healthy-looking people unless the scene was one of poverty.
Gradually over the intervening decades, the emphasis from public health “advocates” has been a recommendation for use of “lowfat” diets for just about any disease state, and certainly as the accepted and appropriate treatment for obesity, which has become a major health problem in the United States. Not all researchers accept the belief that fat intake causes obesity, and it has been pointed out that “. . . there is no conclusive evidence from epidemiologic studies that dietary fat intake promotes the development of obesity independently of total energy intake.”2 The recognition by some researcher that it is the energy content of the diet that is important matches the understanding of clinicians half a century ago. Nevertheless the common recommendation continues to be a “lowfat” diet for treating obesity in spite of the numerous research papers reporting better results with the low-carbohydrate diet.3,4
The low-carbohydrate diet by definition cannot be a lowfat diet because there is a limit to the amount of protein one can eat. Thus, carbohydrate calories are normally substituted for fat calories in the various diets, and vice versa.
When researchers examined the diets of older adults who had successfully maintained “lower-fat” intakes for five or more years, they found that “lower” meant on average 26 percent (+/- 7 percent) calories as fat and that the original diets had been about 44 percent (+/- 6 percent).5 Even the American Dietetic Association (ADA) recommends that “diets should provide moderate amounts of energy from fat (20 percent to 25 percent of energy)” and noted that the more restrictive level of 15 percent offered no advantage. However, since typical diets have been found to be closer to 35 percent of energy as fat, even their recommendation of 20-25 percent represents a lowfat approach.6
When you lower the amount of fat in the diet, you must raise something else. That something else is usually carbohydrate, and invariably today it would be mostly simple carbohydrates such as white flour, corn syrup or refined sugar. High levels of carbohydrate in a diet do not provide the satiety that natural fats do, and the result is that there is a tendency to overeat carbohydrates. Today the carbohydrates come with many undesirable additives and are frequently missing many nutrients. But if the carbohydrates are similar to those available 60 years ago, (that is, whole grains and complex sugars) the situation might not be too bad for a short time.
What happens when a person changes his diet from the typical American diet of processed foods to the recommended lowfat diet containing lots of whole grains and vegetables? First the body is no longer taking in all the excess omega-6 and trans fats that are in processed foods. And, he is replacing foods loaded with sugars and additives with more natural foods containing a lot of vitamins and minerals. But most importantly, the body turns the excess carbohydrates into saturated fat. This saturated fat can replace omega-6 and trans fatty acids in the tissues, which is advantageous and helps the patient feels better. A high-carbohydrate diet is really a high-saturated-fat diet and the various processes on the cellular level work better when there are ample saturated fatty acids available.
Under experimental conditions of overfeeding simple sugars (sucrose and glucose) in a diet that provided 40 percent of energy as fat, the researchers found that the carbohydrate was oxidized and turned into fat in such a manner that the loss of fat was prevented.7 In other words, a diet high in both fats and carbohydrates will cause weight gain, especially when these are processed vegetable oils and refined carbohydrates.
So what amount of fat should be in a diet? And does is matter what kind of fat there is in the diet?
Over the long term, lowfat diets have not been shown to be advantageous for preventing the diseases they have been recommended for. Most people are at risk for lowered intakes of the important fat-soluble vitamins and other fat-soluble nutrients when they consume lowfat diets for any length of time. So it would seem that the fat content of the diet of yesteryear, with an average of 35-40 percent of energy as fat, makes sense. For those who are prone to hypoglycemia, seizures or who are recovering from an operation or illness, the percent of energy from fat should be higher. Growing infants and children also need a higher proportion of fat in the diet. Whatever level of fat works for an individual, it should be a mixture of natural fats that were common in the diets 60 and more years ago.
Perhaps the best way to lose unwanted weight (excess weight in the form of fat, that is) is to change the type of fat in the diet to the type of fat found in the coconut. New research from McGill University in Canada has shown that consuming medium-chain triglycerides (C8, C10, C12, and C14), the type found in coconut oil, leads to an increase of endogenous oxidation of long-chain saturated fatty acids. They note that this “suggests a role for medium chain triglyceride fats [such as coconut oil] in body weight control over the long term.”8
- K. Mitchell. Food in Health and Disease: Preparation, Physiological Action and Therapeutic Value, Third Edition. F.A. Davis Co., Philadelphia 1944.
- Seidell JC. Dietary fat and obesity: an epidemiologic perspective. Am J Clin Nutr 1998 Mar;67(3 Suppl):546S-550S.
- Rabast U, Schonborn J, Kasper H. Dietetic treatment of obesity with low and high-carbohydrate diets: comparative studies and clinical results. Int J Obes 1979;3(3):201-11.
- Golay A, Eigenheer C, Morel Y, Kujawski P, Lehmann T, de Tonnac N. Weight-loss with low or high carbohydrate diet? Int J Obes Relat Metab Disord 1996 Dec;20(12):1067-72.
- Abusabha R, Hsieh KH, Achterberg C. Dietary fat reduction strategies used by a group of adults aged 50 years and older. J Am Diet Assoc 2001 Sep;101(9):1024-30.
- J Am Diet Assoc 2000 Dec;100(12):1543-56. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance.
- McDevitt RM, Bott SJ, Harding M, Coward WA, Bluck LJ, Prentice AM. De novo lipogenesis during controlled overfeeding with sucrose or glucose in lean and obese women. Am J Clin Nutr 2001 Dec; 74:737-746.
- Papamandjaris AA, White MD, Raeini-Sarjaz M, Jones PJ. Endogenous fat oxidation during medium chain versus long chain triglyceride feeding in healthy women. Int J Obes Relat Metab Disord 2000 Sep;24(9):1158-66
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Winter 2001.