Friday, July 18, 2008

Diet & Nutrition 1 - The Low Fat Diet Canard

The statue above is the Venus of Willendorf. It is 30,000 years old, predating the written record by some 20 millenium. But it is an anatomically correct statue of an obese woman, thus letting us know that the problem of obesity has been with us for a long time - and apparently was possible even on a hunter gatherer diet.

As I find interesting news on diet, nutrition and exercise, I will try to start to start posting it as part of a running series. "Low Fat" diets have been a fad for years and companies have been cashing in on "low fat" foods of all stripes. But fat plays a critical role in depressing appetite and the proper mix of fats (omegas 3, 6 and 9) plays a crucial role in long term health. At any rate, it is no surprise to learn today that a two year study of 322 people by researchers at Ben-Gurion University of the Negev has found that the "Mediterranian" Diet and the low carb diet, both of which are moderately high in fats, are safer and more effective at creating sustained weight loss than the low fat diet typically recommended by physicians.

This from an article on the study:

. . . In the two-year study, 322 moderately obese people were intensively monitored and were randomly assigned one of three diets: a low-fat, calorie-restricted diet; a Mediterranean calorie-restricted diet with the highest level of dietary fiber and monounsaturated/saturated fat; or a low-carbohydrate diet with the least amount of carbohydrates, highest fat, protein, and dietary cholesterol. The low-carb dieters had no caloric intake restrictions.

Although participants actually decreased their total daily calories consumed by a similar amount, net weight loss from the low-fat diet after two years was only 6.5 lbs. (2.9 kg) compared to 10 lbs. (4.4 kg) on the Mediterranean diet, and 10.3 lbs. (4.7 kg) on the low-carbohydrate diet. "These weight reduction rates are comparable to results from physician-prescribed weight loss medications," explains Dr. Iris Shai, the lead researcher.

The low-fat diet reduced the total cholesterol to HDL ratio by only 12 percent, while the low-carbohydrate diet improved the same ratio by 20 percent. Lipids improved the most in the low-carbohydrate, with a 20% increase in the HDL ("good") cholesterol and, 14% decrease in triglycerides. In all three diets, inflammatory and liver function biomarkers was equally improved. However, among diabetic participants, the standard low-fat diet actually increased the fasting glucose levels by 12mg/dL, while the Mediterranean diet induced a decrease in fasting glucose levels by 33mg/dL.

In addition to the findings, this two-year study is also significant because of the relatively large number of participants coupled with a low drop-out rate – 95 percent were in the study after one year and 85 percent were still participating after the second.

Dr. Iris Shai is a researcher at the S. Daniel Abraham International Center for Health and Nutrition in the Department of Epidemiology at Ben-Gurion University of the Negev. She conceived the study with Dr. Stampfer, the senior author, while she was a Fulbright fellow at Harvard School of Public Health and Channing Laboratory in Boston, Massachusetts.

. . . "Clearly, there is not one diet that is ideal for everyone," Shai concludes. "We believe that this study will open clinical medicine to considering low-carb and Mediterranean diets as safe effective alternatives for patients, based on personal preference and the medical goals set for such intervention. Furthermore, the improvement in levels of some biomarkers continued until the 24-month point, although maximum weight loss was achieved by 6 months. This suggests that healthy diet has beneficial effects beyond weight loss."

Read the entire article.

Update: I have decided to open up a new blog on this topic rather than run it as a series here. You can find this post crossposted at the new blog, Wolf Health.


SnoopyTheGoon said...

Forces you to process a lot of veggies, though. Tough call...

Thanks for the link. Reciprocated.

vinny said...

A low fat diet is not for everyone; especially for the diabetic, the problem would be that a diet low in fat will mean a diet high in carbohydrates and consequently high intake of simple sugars. Nevertheless you have to be very careful when such small studies are generalized to large populations. One remarkable item from this study is that all groups managed to restict their diet to about the same amount of calories, even in the non-calorie restricted group. This is an amazing achievement because the human body will respond to weight loss by increasing the desire to eat. For this reason our weight remains the same year to year. This suggests that there were other intervention methods employed on the study population. What was their dropout rate? Since this was a small study, a dropout rate of 10% might make the difference between statistically significant results and random fluctuations. These are some of my reservations before drawing conclusions from above data. BTW, doctors don't recommend a low fat, high sugar diet anymore. This commonly taught food pyramid in elementary school was essentially an invention of one guy in 1940's based on his preferences and for some reason still survives in popular culture. High fiber is recommended from prevention point of view; it is associated with decreased rate of cancer. The typical high fat diet is the KFC, McDonald, and donut diet which is also high in sugar and very low in carbohydrates. It is this diet that is favored by diabetic population, and precisely this diet that is strongly discouraged by the medical profession. If you wish to reduce your calories and want to eat lesser amount of whole fat yogurt than the equivalent in calories low fat yogurt, I am not that either strategy is better. Just reducing your calories is probably the main benefit.

shoprat said...

Interesting info. Thanks.

GW said...

Very good points, Vinny. Perhaps my title was a bit too flippant. Nothing I will ever right will be in support a fast food meal, regardless of the diet.

I did not realize that docs had moved away from the low fat diets. That is good news. But what have they moved to? Something like the Med diet I would hope.