Dietary Intervention Randomized Controlled Trial (DIRECT) Group, N Engl J Med 2008 359: 229-241

This interesting study from Israel, comparing three commonly recommended diets, was the feature report this week by Norman Swan on Radio National’s Health Report

Low-Fat Diet

The low-fat, restricted-calorie diet was based on American Heart Association guidelines, with an energy intake of 1500 kcal per day for women and 1800 kcal per day for men. 30% of calories were from fat, 10% of calories were from saturated fat, and there was an intake of 300 mg of cholesterol per day. The participants were counseled to consume low-fat grains, vegetables, fruits, and legumes and to limit their consumption of additional fats, sweets, and high-fat snacks.

Mediterranean Diet

The moderate-fat, restricted-calorie, Mediterranean diet was rich in vegetables and low in red meat, with poultry and fish replacing beef and lamb. We restricted energy intake to 1500 kcal per day for women and 1800 kcal per day for men, with a goal of no more than 35% of calories from fat; the main sources of added fat were 30 to 45 g of olive oil and a handful of nuts (five to seven nuts) per day.

Low-Carbohydrate Diet

The low-carbohydrate, non–restricted-calorie diet aimed to provide 20 g of carbohydrates per day for the 2-month induction phase and immediately after religious holidays, with a gradual increase to a maximum of 120 g per day to maintain the weight loss. The intakes of total calories, protein, and fat were not limited. However, the participants were counseled to choose vegetarian sources of fat and protein and to avoid trans fat. The diet was based on the Atkins diet

There were 322 moderately obese participants, (82% men!), all from the one workplace in Israel.

Key findings

The study period was 24 months.
Participants lost weight on all three diets.

All diets improved HDLs and overall lipid profile, with the Low Carb having the best results (the low carb diet increased HDL by 20%).

The Mediterranean diet had the most significant decrease in fasting BSLs, but the low carb diet had the most significant lowering of HbA1C.

Comments, Lessons and Practice Points

What do you think about this study and the lessons for our patients?

Choice of Diet

Traditionally we have recommended a low-fat diet to our patients who want to lose weight. However, this study demonstrated that low carb or Mediterranean style diets are probably more effective. The low carb diet is more difficult to stick to, but most people managed the 24 months regime. It was the only diet that was not calorie restricted.

Patients therefore should choose the style of diet that most fits their usual preferences – and stick to it!

French Women Don’t Get Fat

There was however a more significant difference between the diets for the women participants (of which there were only 45). The Mediterranean Diet was significantly more effective.

The low-fat /low-glycaemic-index diet was not one of the options tested but may appear to be a most appropriate recommendation. What do dietician’s think?

Expectations for Weight Loss

Many of our patients want to go from a size 16 to a size 10. This study reminds us that even strict dietary regimes lead to relatively moderate weight loss, with women on the Meditarranean diet doing best with about ‘one stone’ off after 24 months. Patients emabarking on a new regime should have realistic aims so as to become discouraged.

Maintaining Weight Loss

Most interestingly maximum weight loss was achieved at 6 months. The next 18 months needs to be considered ‘maintenance’ with some weight regain. Patients need to be reminded that the diet they need to lose the weight is the same diet they need to keep it off. If they consider dieting to be a temporary lifestyle change, they will experience the well known yo-yo phenomenon with net weight gain.

I’d welcome your comments and thoughts.

In Rethinking Thin, Gina Kolata, a veteran New York Times science reporter uses case studies to illustrate her general point that “very few people lose substantial amounts of weight and keep it off” because genetic factors play a large role in determining how much a given person will weigh as an adult.

In Mindless Eating, Wansink, a marketing professor at Cornell University who has studied consumers’ food-related decisions for decades, focuses on the sort of gradual, modest weight loss that Kolata concedes is achievable. Declaring that “the best diet is the one you don’t know you’re on,” he urges small changes in everyday behavior that over the course of a year can result in a weight loss of 10 to 25 pounds.

Wansik talks about paying attention to food and avoiding mindless eating.

 “It takes up to 20 minutes for our body and brain to signal satiation,” he notes, and Americans often finish their meals in less time than that. Instead of internal signals we rely on external cues to tell us when we’re done: Is the plate clean? Is everyone else done? Is there more in the serving dish?

To counteract such cues, Wansink recommends such tactics as using smaller plates (which make portions seem larger), keeping serving dishes in the kitchen (which discourages second helpings), replacing short, wide glasses with tall, thin ones (which make drinks seem bigger), keeping food scraps and bones on your plate (which reminds you how much you’ve eaten), and dividing snacks from big packages into smaller bags or plastic containers (which discourages you from devouring the entire package).