I picked this paper up from George Henderson via twitter
Effects of dietary fat on gut microbiota and faecal metabolites, and their relationship with cardiometabolic risk factors: a 6-month randomised controlled-feeding trial
which is part of the same study as this one
Effects of Macronutrient Distribution on Weight and Related Cardiometabolic Profile in Healthy Non-Obese Chinese: A 6-month, Randomized Controlled-Feeding Trial
The study is amazing. The researchers provided all of the food to all of the participants for six months. The only fat source was soybean oil. It could almost be a rodent study. This is what the study says:
"The three diets were isocaloric, the primary distinguishing feature being their fat and carbohydrate content (Table 1). By replacing a proportion of energy derived from carbohydrates (white rice and wheat flour, the most consumed carbohydrate sources in China contributing to 70% and 17% total carbohydrate respectively) with fats (soybean oil, the most consumed edible oil in China rich in unsaturated fatty acids)..."
Just a few things to point out: The diets were isocaloric. No one was allowed to select their calorie intake. Blokes got just over 2000kcal/day, women got 1700kcal/day. Some supplementary fruit was allowed, to be recorded as and when eaten.
Here are the baseline diets for each of the intervention groups:
Here is what the intervention diets looked like:
Particularly note the exact match of calories normally eaten at baseline compared with that supplied by the study intervention, which was utterly accurately measured out in the study kitchen.
What happened to the weights during the intervention? This did:
The yellow line is 24% PUFA, red is 18% PUFA and blue is 11% PUFA, all by energy intake.
The first thing to say is that all participants lost weight. I guess that has something deep to say about the accuracy of three day dietary records!
However the weight loss was far from uniform and was clearly inversely related to the level of PUFA in the diet. Less PUFA, greater weight loss, 2kg in eight weeks for the lowest PUFA group. This cannot be explained by reduced food intake because all food calories were provided, in exact amounts, by the study kitchens. Diets were isocaloric...
Protons would suggest that the higher the PUFA content the more dietary fat was "lost" in to adipocytes then not subsequently released. From the cico-tard point of view just over a kilo of fat was "not released" from adipocytes over eight weeks of weight loss in the high PUFA vs the low PUFA group. That's 1000g over 56 days or just under 20g/day. This would have to be countered by a decrease in metabolic rate, in NEAT or specific activity. Or more cheating, recorded or not recorded. The study authors assure us there was no cheating.
After eight to 12 weeks all subjects started to regain weight. The regain slope suggests about a kilo per year on a rigidly fixed calorie, weight reducing food intake.
These people were 23 years old and weighed 60kg. If they stuck with this diet over 30 years they might end up at 90kg. Of course this wouldn't happen if they really stuck with the diet. As weight gain tried to continued on a fixed calorie intake, hunger would increase.
You cannot argue with hunger for 30 years. The subjects would break the diet and eat more. This manifest lack of "willpower" or gross "gluttony" would take the blame for the increased weight gain, which would be blamed on the increased calorie intake.
But the weight regain was already there on a rigidly fixed calorie intake. A calorie intake which gave eight weeks of initial weight loss. This still gave a progressive weight gain with no declared increase in caloric intake.
The beauty of PUFA and the Protons concept.
NB It is difficult to emphasise how good this study is. Just ignore anything the authors have to say.