It’s the perennial diet dilemma: What diet is best for weight loss?
This debate has flared for decades, fueled most recently by anecdotal, though plentiful, claims of outsized successes with low-carbohydrate diets like the Atkins’ program and the South Beach Diet
A new Israeli study, dubbed the Dietary Intervention Randomized Controlled Trial (DIRECT) Trial, performed by Drs. Iris Shai and colleagues, has shown that of three different diet strategies studied, a low-carbohydrate diet was most successful at achieving weight loss.
In this newest of studies comparing the various strategies, 322 participants followed one of three diets over two year period. Compared head-to-head, the (mean) weight loss in each group was:
• 2.9 kg (6.4 lbs) for the low-fat group
• 4.4 kg (9.7 lbs) for the Mediterranean-diet group
• 4.7 kg (10.3 lbs) for the low-carbohydrate group
(Average age 52 years at start; average body-mass index, or BMI, 31.)
The conclusion was that the low-carb diet performed the best, with 60% greater weight loss, with the Mediterranean diet a close second.
The diets
The low-fat diet was based on American Heart Association advice, with 30% of calories from fat (10% from saturated fat) and food choices weighted towards low-fat grains, vegetables, fruits, and legumes and limited additional fats, sweets, and high-fat snacks; calorie intake of 1500 kcal per day for women and 1800 kcal per day for men was encouraged.
The Mediterranean diet was a moderate-fat diet rich in vegetables, with reduced red meat, and poultry and fish replacing beef and lamb. Total calories from fat of 35% per day or less was the goal, with most fat calories from olive oil and a handful of nuts. Like the low-fat program, calories were limited to 1500 kcal per day for women, 1800 kcal per day for men.
The low-carbohydrate diet was patterned after the popular Atkins’ program, with 8% of participants achieving the ketosis that Dr. Atkins’ advocated as evidence that a fat-burning metabolism was activated, rather than sugar-burning as fuel. For the 2-month “induction phase,” 20 grams of carbohydrates per day was set as the goal, followed by 120 grams per day once the weight goal was achieved. Unlike the other two diets, calories, protein and fat were unlimited.
Metabolic changes
The low-carbohydrate diet exerted the greatest change in cholesterol, or lipid, panels: increased HDL 8.4 mg/dl vs. 6.3 mg/dl on low-fat; the triglyceride response was the most dramatic, with a reduction of 23.7 mg/dl vs. 3.7 mg/dl on low-fat. Interestingly, the LDL cholesterol-reducing effect of all three diets was modest, with the most reduction achieved by the Mediteranean diet.
The inflammatory measure, C-reactive protein (CRP), was reduced most effectively by the low-carb and Mediterranean diets, least by the low-fat diet. HbA1c, a measure of long-term blood sugar, dropped significantly more on the low-carb diet.
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