In September 1998, the American Heart Association released a report which claims very low fat diets (<15%) may pose serious health risks for some people, and that such diets are not recommended for the general population. The report claims that clinical trials haven’t shown such diets are advantageous and safe.
What do studies say?
All clinical trials to date, using only the AHA’s dietary guidelines or even their more stringent Step 2 Diet (with saturated fat reduced to 7% or less) which measured atherosclerotic plaques, have found that the disease still progresses in most subjects.
By contrast, a very low fat diet was demonstrated to regress atherosclerosis in most patients with advanced disease. Another study found that a very low fat diet greatly reduced mortality over 12 years in patients who had a previous heart attack. To date, no one has shown such a remarkable decline in overall mortality with a diet higher than 15% fat.
Effects of A High Fat Diet
The percentage of dietary fat plays little, if any, role in determining serum cholesterol level and whether atherosclerosis develops. What is most important, is the type of fat and the type of carbohydrate in the diet - not the percentage of each.
There are some disadvantages to diets higher in fat. For example, diets higher in fat elevate postprandial triglycerides (TGs) and clotting factor VII (CFVII). For someone with significant atherosclerosis, increased CFVII can promote thrombus formation and an increased risk of a fatal heart attack and ischemic stroke for several hours after every high fat meal. Elevated postprandial TGs also leads to the production of a more atherogenic lipoprotein profile.
Another problem with diets higher in fats is that they are usually much more calorie-dense than diets higher in carbohydrate or protein. Most evidence indicates that a high-calorie-dense diet, not ratios of macronutrients, promotes overeating and weight gain. Weight gain increases the risk of many factors that promote atherosclerosis and heart attacks, such as increased LDL, triglycerides, insulin and lower HDL.
Subjects who adhere to a very low-fat diet almost always lose weight and see dramatic improvement in their blood lipids.
Interpretation Tricky Here
The co-author of the recent AHA report, Dr. Lichtenstein, has published two studies that showed potentially adverse metabolic effects on a very low-fat diet compared to a 30% fat diet but only when both were fed at the same calorie level.
It was only when the subjects on the very low-fat diet were required to eat more than they wanted that they experienced a big rise in triglycerides and a major drop in HDL. When the subjects on the very low-fat diet were not required to eat as many calories, their 24 hour triglycerides were much lower than people eating the 30% fat calorie diet and their HDL dropped only slightly.
Lower HDLs on very low-fat diets may not be bad news since fractional clearance rates of cholesterol transported back to the liver are more rapid on these diets.
Percent of Fat Should Not Be The Focus
The AHA is correct to warn
consumers that a diet high in fat-free products composed largely of sugar and or white flour can have adverse metabolic effects. But by focusing their press releases on the percent of fat rather than on the types of fats and carbohydrates they’ve only added to the public’s confusion about how to reduce America’s number one killer, cardiovascular disease.
What should be avoided is a diet high in refined, processed and concentrated carbohydrates, which are calorically dense and nutrient poor. These types of fat-free products are unlikely to promote either weight loss or good health.
Consumers need to be warned about the dangers of diets rich in refined carbohydrates, saturated fats, salt and cholesterol, as opposed to percent of fat, for preventing heart disease. We certainly don’t want to discourage people from consuming non-fat dairy products and more fruits, vegetables, whole grains and beans, most of which have less than 15% calories from fat.
For a comprehensive review of the advantages of a very low-fat diet for treating and preventing hypercholesterolemia, see Kenney, JJ Clin Appl Nutr 1992;2:81-93.
200 Not Low Enough
While a serum cholesterol level of 200 mg/dl is considered desirable by the AHA?and NCEP, many thousands of Americans with this cholesterol level have heart attacks and strokes and die every year.
On September 9, 1998, Dr. Antonio Gotto, the dean and medical provost for Cornell University Medical College, told a gathering of cardiologists and nutritionists that the current cholesterol guidelines are not stringent enough to stop the progression of atherosclerosis (Reuters news service).
Over the past 35 years, data from the Framingham, MA study have demonstrated that the safest levels are a serum cholesterol level of no more than 160 mg/dl and a LDL of less than 100 mg/dl.
The bottom line: have your cholesterol checked regularly. Strive to get your cholesterol closer to 160 than 200. Increasing consumption of high-fiber foods and decreasing consumption of foods high in saturated fat and animal protein will help.
Dr. Jay Kenney, PhD, RD is the Nutrition Research Specialist for the Pritikin Longevity Centers and he is on the Board of Directors for the National Council Against Health Fraud.
If you add about 3 tablespoons of chocolate syrup to a glass of whole milk, you will change the percent of calories from fat from 50% to 25%.
Judy’s passion for cooking began with helping her grandmother make raisin oatmeal for breakfast. From there she earned her first food service job at 15, was accepted to the world famous Culinary Institute of America at 18 (where she graduated second in her class), and went on to the Fachschule Richemont in Switzerland where she focused on pastry arts and baking. But after learning that the quality of a croissant directly varies with how much butter it has, Judy sought to challenge herself by coming up with recipes that were as healthy as they were tasty.
Judy received The Culinary Institute of America’s Pro Chef II certification, the American Culinary Federation Bronze Medal, Gold Medal, and ACF Chef of the Year. Her enthusiasm for eating nutritiously and deliciously leads her to constantly innovate and use the latest in nutritional science to guide her creativity, from putting new twists on fajitas to adapting Italian brownies to include ingredients like toasted nuts and cooked honey. Judy’s publishing company, Food and Health Communications, is dedicated to her vision that everyone can make food that tastes as good as it is for you.