This one, A Palaeolithic diet improves glucose tolerance more than a Mediterranean-like diet in individuals with ischaemic heart disease, is highly interesting for many reasons. Rather than using a single control group who is told to eat their "usual" diet, two groups were each assigned to healthy diets (Mediterranean-type and Paleolithic-type). Both groups were told they were on a healthy diet and were not told what the other group was on, presumably controlling for the "placebo effect" and the fact that control groups typically adjust their diets to be the "healthy diet" of the time when enrolled in such trials.
Surprise surprise. Both groups lost weight (even though calories weren't restricted) and belly fat, increased their glucose tolerance and improved their vital stats overall. Both groups naturally decreased their caloric intake over the 12-week period. (Dietary guidelines for each group are at the end of the post.)
The portion I found most interesting was this
Quote:
Thus, waist loss increased with increasing intake of fruits and decreasing intake of cereals, associations which explained most of the group difference in waist loss.
The Paleo-type group, which ate no cereals (including rice in this study), lost, on average, 2.7cm (1in) more from their waist over a 12-week period than the Mediterranean-type group. They also lost an average of 1.2kg (2.6lb) more. The researchers concluded, after examining the data, that the differences in weight loss could be correlated to the total calorie consumptions of the two groups (Paleo-like 1,344 on average, Mediterranean-like 1,795 on average). Thus, waist loss increased with increasing intake of fruits and decreasing intake of cereals, associations which explained most of the group difference in waist loss.
Obvious problems: The "Paleo" diet proposed differs greatly from other "Paleo" diets that exist. The "Mediterranean" diet given to patients was closer to a generic "healthy diet" than a true "Mediterranean" diet program. The sample size was also far too small to develop scientifically meaningful results.
What the study did do, though, was create an environment that successfully tested the idea that grains impede the burning of fat. Some researchers have suggested that Omega-6 fats-found in high concentrations in grains-contribute to the creation of belly fats while Omega-3 fats-found in high concentrations in green leaves and fruits-contribute to effective metabolism.
The diets...
Mediterranean-type
-------------------
based on whole-grain cereals, low-fat dairy products, potatoes, legumes, vegetables, fruits, fatty fish and refined fats rich in monounsaturated fatty acids and alpha-linolenic acid
Paleo-type
----------
increase their intake of lean meat, fish, fruits and vegetables and to avoid all kinds of dairy products, cereals (including rice), beans, sugar, bakery products, soft drinks and beer. The following items were accepted in limited
amounts for the Palaeolithic group: eggs (one or fewer per day), nuts (preferentially walnuts), potatoes (two or fewer medium-sized per day), rapeseed or olive oil (one or fewer tablespoons per day). The intake of other foods was not restricted and no advice was given with regard to proportions of food categories (e.g. animal vs plant foods).