A great study was just published in the Journal of the American College of Cardiology:
Metabolic effects of weight loss on a very-low-carbohydrate diet compared with an isocaloric high-carbohydrate diet in abdominally obese subjects.
88 obese adults with metabolic syndrome were placed on either of two diets:
1) A very low-carbohydrate, high-fat diet (VLCHF): 4% calories from carbohydrates (truly low-carb); 35% protein; 61% fat, of which 20% were saturated. In the first 8 weeks, carbohydrate intake was severely limited to <20 grams per day, then <40 grams per day thereafter.
2) A high-carbohydrate, low-fat diet (HCLF): 46% calories from carbohydrates; 24% protein; 30% total fat, of which <8% were saturated.
Both diets were equal in calories (around 1400 calories per day--rather restrictive) and participants were maintained on the program for six months.
At the end of the six month period, participants on the VLCHF diet lost 26.4 lb, those on the HCLF diet 22.2 lbs (though the difference did not reach statistical significance). Thus, both approaches were spectacularly successful at weight loss.
Surprisingly, blood pressure, blood sugar, insulin and insulin sensitivity (a measure called HOMA) were all improved with both diets equally. Thus, these measures seemed to respond more to weight loss and less to the food composition.
Lipids differed between the two diets, however:
Total cholesterol: initial 208.4 mg/dl final 207.7 mg/dl
LDL: initial 125 mg/dl final 123 mg/dl
HDL: initial 55 mg/dl final 64.5 mg/dl
Triglycerides: initial 144 mg/dl final 74 mg/dl
Apoprotein B: initial 98 mg/dl final 96 mg/dl
Total cholesterol: initial 208.4 mg/dl final 187.5 mg/dl
LDL: initial 126 mg/dl final 108 mg/dl
HDL: initial 51 mg/dl final 54.5 mg/dl
Triglycerides: initial 157.6 mg/dl final 111 mg/dl
Apoprotein B: initial 100 mg/dl final 95 mg/dl
Some interesting differences became apparent:
--The VLCHF diet more effectively reduced triglycerides and raised HDL.
--The HCLF diet more effectively reduced total and LDL.
--There was no difference in Apo B (no statistical difference).
The investigators also made the observation that individual responsiveness to the diets differed substantially. They concluded that both diets appeared to exert no adverse effect on any of the parameters measured, both were approximately equally effective in weight loss with slight advantage with the carbohydrate restricted diet, and that lipid effects were indeed somewhat different.
What lessons can we learn from this study? I would propose/extrapolate several:
When calories are severely restricted, the composition of diet may be less important. However, when calories are not so severely restricted, then composition may assume a larger role. When calories are unrestricted, I would propose that the carbohydrate restriction approach may yield larger effects on weight loss and on lipids when compared to a low-fat diet.
The changes in total cholesterol are virtually meaningless. Part of the reason that it didn't drop with the VLCHF diet is that HDL cholesterol increased. In other words, total cholesterol = LDL + HDL + trig/5. A rise in HDL raises total cholesterol.
Despite no change in Apo B, if NMR lipoprotein analysis had been performed (or other assessment of LDL particle size made), then there would almost certainly have seen a dramatic shift from undesirable small LDL to less harmful large LDL particles on the VLCHF diet, less change on the HCLF diet.
The lack of restriction of saturated fat in the VLCHF that failed to yield adverse effects is interesting. It would be conssistent with the re-analysis of saturated fat as not-the-villain-we thought-it-was put forward by people like Gary Taubes (Good Calories, Bad Calories).
In the Track Your Plaque experience, small LDL is among the most important measures of all for coronary plaque reversal and control. Unfortunately, although this study was well designed and does add to the developing scientific exploration of diet, it doesn't add to our insight into small LDL effects. But if I had to make a choice, I'd choose the low-carbohydrate, high-fat approach for overall benefit.