A landmark study comparing Low fat, Low carb and Mediterranean diets over a 2 year period has shown low carb and Mediterranean diets to be favorable alternatives to low fat. The study looked at weight loss, blood lipids, glycemic control and inflammation.
Let's explore the study details and see what applications may arise from it.
Study Details
Participants:
Middle aged (mean age 52) and mildly obese (BMI 31) randomized to 3 diets:
- Low fat/restricted calorie (1500 cal - women, 1800 cal - men)
- Mediterranean/restricted calorie (same caloric intake as low fat)
- Low carb - no restriction on calories
Results
Adherence:
After two years, adherence to their respective diets ranged from more than 90% in the low-fat group, to 85% in the Mediterranean diet group, to 78% in the low-carb group.
Side note: Participants in the trial ate their main meal of the day--lunch--in the workplace cafeteria, where food choices were carefully controlled and labeled. On-site dieticians worked regularly with participants to help them adhere to their diets.
Weight Loss:
| Group | Low-fat (lbs) | Mediterranean (lbs) | Low-carb (lbs) |
| All patients | -6.4 | -9.7 | -10.3 |
| All completers | -7.3 | -10.1 | -12.1 |
| Men | -7.5 | -8.8 | -10.8 |
| Women | -0.2 | -13.6 | -5.3 |
It's interesting that women (oddly, there weren't very many of them in the study) fared far better in the Mediterranean group.
Lipid Changes:
| Parameter | Low-fat (mg/dL) | Low-carb (mg/dL) | Mediterranean (mg/dL) |
| HDL | +6.4 | +8.4 | +6.3 |
| LDL | -0.05 | -3.0 | -5.6 |
| Triglycerides | -2.8 | -23.7 | -21.8 |
| Total cholesterol/HDL ratio | -0.6 | -1.1 | -0.9 |
Inflammation:
The level of high-sensitivity C-reactive protein decreased significantly only in the Mediterranean-diet group (21%) and the low-carbohydrate group (29%), during both the weight-loss and the maintenance phases.
Blood Glucose/Insulin:
Among the 36 participants with diabetes, only those in the Mediterranean-diet group had a decrease in fasting plasma glucose levels. Insulin levels decreased slightly in all groups, with no significant differences between them.
What to do with this
By now you are probably sick of hearing about these studies. Perhaps the best conclusion that can be drawn from this study is one that most of us know already - that there are different paths to different dietary patterns can produce favorable health results.
The study is a comprehensive one, but not without its flaws. The adherence rates are artificially high due to the partially controlled environment and the consultations with dietitians. Also, energy expenditure was not factored in, which can account for a significant piece of the health/weight loss picture. I also would have liked to see body composition measurements in addition to scale weight.
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