There is nothing new about our love of fat and sugar. Evolutionary we have a strong inclination to eat these foods because they are rich sources of calories and, consequently -energy. We all know that fat makes you fat, and is often recognised as the cause, since any type of fat packs more than twice the calories of carbohydrate, sugar and protein.
Recent dietary guidelines for reducing the risk of cardiovascular disease have suggested replacing saturated fat with other caloric nutrients, such as carbohydrates. However, processed carbohydrates, which many people eat today in place of fat, may increase the risk of obesity, diabetes and heart disease more than fat does. It is down to insulin – the hormone that regulates the metabolic impact, raises cholesterol levels and thickens the arteries, and problems with insulin come, not from eating fats, but carbohydrates like sugar.
The meta-analysis, published in the American Journal of Clinical Nutrition, combines data from several studies that compared the daily food intake of nearly 350,000 people against their risk of developing cardiovascular disease. The analysis1, found NO association between the amount of saturated fat consumed and the risk of heart disease. Though saturated fat boosts blood levels of “bad” LDL cholesterol, it also increases “good” HDL cholesterol. The further study2 of moderately obese men and women found that the individuals on the low-carb diet ate the most saturated fat; however they ended up with the healthiest ratio of HDL to LDL cholesterol and lost twice as much weight as people on Mediterranean or low-calorie high-carb diets.
So, what should we eat?
Our genes are almost identical to those in people living centuries ago, and ancient human diet provides clues to what might be the best diet for most people. Meal plans fairly high in quality proteins and low in processed carbohydrates would seem to be what most people are best suited to. Saturated fat in form of eggs and dairy are fine, and cheese might actually provide heart benefits. The red meat should be eaten in moderation, because it may boost the risk of heart disease and cancer for reasons unrelated to saturated fat. Eat lots of vegetables, because their role in disease prevention is so well established. Cut back on carbohydrates, but don’t eliminate them. If you eat bread, whole wheat/meal bread, in which the seeds are visible and plentiful, is the best. The suggestion is to adjust carb intake to your weight, blood sugar, and activity level. If they are good on all three counts, you can probably consume a little more carbohydrates. However if you are overweight, have high blood sugar, and are inactive, you should be getting you carbs from high-fibre vegetables, not grains.
1 Siri-Tarino PW, Sun Q, H FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. American Journal of Clinical Nutrition, 2010;91: 502-509.
2Foster GD, Wyatt HR, Hill JO, et al. Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet: A Randomized Trial. Annals of Internal Medicine, 2010; 153:147-157; Shai I, Schwartzfuchs D, Henkin Y, et al. Weight loss with a low-carbohydrates, Mediterranean, or low-fat diet. New England Journal of Medicine, 2008;359: 229-241.