Which is the Best Diet?
Several weeks ago The New England Journal of Medicine featured an article that should be of interest to all who are watching their weight. The article reported on a weight loss study comparing three popular diets: a low fat diet (American Heart Association diet), low carbohydrate diet (Atkins) and the Mediterranean diet. The goal was to find which diet worked best. Study subjects were randomly assigned to one of the three diets and were followed for two years, quite a long time for a clinical study. Results? The findings showed the low carbohydrate and Mediterranean diets resulted in significantly more weight loss over the low fat diet. Previous shorter studies have shown greater weight loss with high protein diets but the long term health consequences were unknown.
There are numerous reasons why individuals lose weight more easily with diets containing more protein. Protein in the diet is digested more slowly than carbohydrate. The chemical bonds between amino acids in protein are more complex than the bonds between sugar molecules in carbohydrates. The digestion of protein consumes more energy than the digestion of carbohydrate – three times the calories are required to digest protein over carbohydrate. And, as everyone who follows a high protein diet will tell you, protein is filling. The high satiety associated with higher protein consumption also explains the results.
Additionally, the study found that the low carbohydrate and Mediterranean diets improved cholesterol profile more than the low fat diet. This may surprise you because the low fat diet was actually designed to lower cholesterol. Cholesterol is naturally present in animal sources, such as meat, egg yolk, cheeses, and milk; logically, by eliminating these from the diet, cholesterol would be expected to fall. Both the low carbohydrate and the Mediterranean diets contain dietary sources of cholesterol. How could it be that the two diets containing sources of cholesterol resulted in lower blood cholesterol than a diet that eliminated cholesterol? The answer to this enigma is: eating high amounts of carbohydrates stimulates the liver to produce cholesterol! Anyone with high cholesterol needs to be aware of this. The olive oil in the Mediterranean diet lowers LDL cholesterol and the omega-3 fat (present in fish) lowers LDL cholesterol and raises HDL cholesterol.
We have become increasingly aware of the role of inflammation in cardiovascular disease and cancer. High-sensitivity C-reactive protein is a blood measurement of inflammation. The level of high-sensitivity C-reactive protein decreased significantly only in the Mediterranean and low carbohydrate groups. The effect seen was quite impressive – a reduction of inflammation of 20%, as measured by C-reactive protein.
Improvement in Blood Sugar
For individuals with diabetes, the study showed a strong benefit in following a Mediterranean diet, with a reduction in fasting blood glucose. All three diets showed benefit on insulin levels.
Everyone wants to know the best diet. With an astounding array of diet books with conflicting advice, a study of this magnitude is important. What gives credence to the study’s findings are: there were a large number of subjects (over 300), the study was of long duration (two years) and there was a low drop-out rate. The study showed quite clearly greater weight loss was achieved with a low carbohydrate or Mediterranean diet, both of which are satisfying. Even more importantly, the weight stayed off and was not regained.