Updated: Apr 12, 2019
In this fifth and final part of this series, I will review some studies that have been done that demonstrate the importance of a diet higher in healthy fats for the purpose of weight loss and for optimizing cardiovascular outcomes.
Before doing so, I wanted to reiterate a point made in an earlier articles (here and here). Before the dietary guidelines of 1977 were released, it was common wisdom, that in order to lose weight, one would need to reduce the consumption of carbohydrates by reducing starches and sugars in particular. These recommendations can be seen as far back as the 1901 edition of The Principles and Practice of Medicine by William Osler, in 1907 by James French in A Text-book of the Practice of Medicine, and in In1925 in H. Gardiner-Hill of London's St. Thomas Hospital Medical School.
"Between 1943 and 1952, physicians from the Stanford University School of Medicine, Harvard Medical School, Children’s Memorial Hospital in Chicago, and from Cornell Medical School and New York Hospital independently published their diets for treating obese patients. All four are effectively identical. Here are the “General Rules” of the Chicago version: 1. Do not use sugar, honey, syrup, jam, jelly or candy. 2. Do not use fruits canned with sugar. 3. Do not use cake, cookies, pie, puddings, ice cream or ices. 4. Do not use foods which have cornstarch or flour added such as gravy or cream sauce. 5. Do not use potatoes (sweet or Irish), macaroni, spaghetti, noodles, dried beans or peas. 6. Do not use fried foods prepared with butter, lard, oil or butter substitutes. 7. Do not use drinks such as Coca-Cola, ginger ale, pop or root beer. 8. Do not use any foods not allowed on the diet and only as much as the diet allows." -Gary Taubes, Why We Get Fat.
A number of doctors studying obesity and effective methods of weight loss met for several conferences in the late 1960's and early 1970s. Reviewing the data available at the time, their work showed that weight loss weight loss as fat appeared to be inversely related to the level of carbohydrates in the diets.
Why am I telling you all this? Decreasing refined carbohydrates and increasing fat content in the diet had long been the standard protocol for losing weight. So, this is not some new, cutting edge diet recommendation, but rather a return back to what we always knew about how to lose weight.
Now, let's look at the various studies that we have available to us that corroborate this idea.
This 2008 study conducted by Meir Stampfer of the Harvard School of Public Health took 322 moderately obese middle aged people and spit them into one of three groups: one low in carbohydrates, one low in fat, and a final Mediterranean diet group.
Overall, the Mediterranean diet group had a lower overall risk of heart disease compared to the low-fat group, ending the study with lower triglycerides, higher HDL cholesterol, lower LDL cholesterol, lower C-reactive protein (an indicator of inflammation), and lower insulin. They also lost more weight, averaging a 10 pound weight loss over the course of the study.
An interesting note- the study's investigators hoped to showcase the Mediterranean diet as the best overall diet for weight loss and cardiovascular risk reduction. Perhaps this is why they were hesitant to publicize results from the third arm of the study, which was the low-carbohydrate diet. Participants in this group of the study, it turns out, ended the study healthiest of all having lost 12 pounds on average and improving the various biomarkers to a greater extent when compared to the other two arms.
One of the largest, best-performed nutritional experiments ever done with nearly 7500 participants. In this study, the control group was told to eat a low fat diet while a second group received a liter of olive oil a week. A third group was told to eat a combination of walnuts, almonds, and hazelnuts. The higher fat groups were not told to restrict calories to compensate for the higher fats. The results were so astounding that the study had to be stoped after 5 years because it was considered unethical to deprive the control group of healthy dietary fats! The added fats reduced risk of heart attacks and deaths by 30 percent!
This 2007 study took 311 overweight, non-diabetic, postmenopausal women and randomized them to one of 4 groups: a low-fat vegetarian Ornish diet, A low-carb (and high fat) Atkins diet, the Zone diet and the LEARN diet. Both the Zone and LEARN were calorie restricted while the other two were calorie unrestricted, meaning the participants could eat as much as they wished within the context of the diet parameters.
Hands down, the high fat group in this study performed much better in every single metric! The participants in the high fat Atkins group lost two times more weight than all the other groups and also had the biggest improvements in risk factors for heart disease, including HDL, insulin, triglycerides, and blood pressure.
1. Ketogenic diet (VLCKD) vs Low fat diet (LFD) - an analysis of results of 13 studies comparing VLCKD vs LFD revealed that "Individuals assigned to a VLCKD achieved a greater weight loss than those assigned to a LFD in the longterm." The authors of the study thus concluded that a VLCKD would serve as a more effective tool in combatting obesity.
2. Low Carb (LC) vs Low fat (LF) diets - This was an analysis of eleven studies that included almost 1400 patients that were followed for a minimum of six months. The LC groups experienced a greater reduction in body weight and a greater increase in HDL cholesterol.
3. Low fat vs high fat diets over the long term (>12 months) - An analysis of 53 randomized controlled trials (RCTs) that compared low carb diets to low fat diets for weight loss showed that "low-carbohydrate interventions led to significantly greater weight loss than did low-fat interventions... In weight loss trials, higher-fat weight loss interventions led to significantly greater weight loss than low-fat interventions... Evidence from RCTs does not support low-fat diets over other dietary interventions for long-term weight loss.
4. Public Health Collaboration Overall, there have been 62 Randomized Controlled trials comparing the effectiveness of low-carb diets versus low-fat diets for weight loss. Of the 62, 2 studies showed no difference between the two groups. 53 of these studies showed that the low-carb group lost more weight while only 7 of the low fat groups lost more weight. Moreover, Of these studies, 31 showed significantly greater weight loss for the low carb group while zero of the low-fat groups demonstrated significantly greater weight loss. (See infographic at the top of the article)
5. Healthline analysis - another great summary of the best available data we have on the topic. Healthline has put together excellent graphs comparing low-carb versus low-fat in the following categories: LDL cholesterol, HDL cholesterol, Triglycerides, weight loss, and compliance with the diets. The overwhelming majority of studies favor low-carb diets in every category! Healthline concluded their article eloquently when they said the following:
"Keep in mind that all of these studies are randomized controlled trials, the gold standard of science. All are published in respected, peer-reviewed medical journals. These studies are scientific evidence, as good as it gets, that low-carb is much more effective than the low-fat diet that is still being recommended all over the world. It is time to retire the low-fat fad!"
This article will appear in the 11th edition of my newsletter, "5 Big Ideas to Upgrade your Health."
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