NEJM — Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet:
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.
| Measure | Low Carb | Mediterranean | Low Fat |
| Mean weight loss for all starters on diet (kg) | 4.7 | 4.4 | 2.9 |
| Mean weight loss for all who stuck to diet (kg) | 5.5 | 4.6 | 3.3 |
| Mean weight loss women (kg) | 2.4 | 6.2 | 0.1 |
| Adherence Rates at 24 months | 78% | 85.3% | 90.4% |
| Waist Circumference Decrease (cm) | 3.8 | 3.5 | 2.8 cm |
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.
3 Comments
If you had to choose one of these three eating patterns to recommend to your patients, the mediteranean diet would certainly the best of these three. This style of eating tends to provide a moderate intake of fat (high in polyunsaturates, including long chain Omega 3 and monounsaturates), with a relatively small percentage of saturated fat. Many of the carbohydrates in this diet would be low glycemic index (pasta, grain/rye breads). Of course, the focus on increasing vegetable intake is also important.
However, the fact remains that recommending a standard “diet” to your patients, is unlikely to result in the sort of sustainable change you are seeking for chronic disease prevention or treatment. Nor, is it likely to address the complex raft of food behaviours or “culture” that paved the road to overwieght/obesity for your patient in the first place.
Any diet that restricts energy will result in weight loss… but the food that comprises any healthy eating plan, should ideally result in a balance (or nutritional Zen!), and should consider your patients health conditions, family history and social eating patterns and behaviours, in order to achieve the best outcome.
Anthony Elliott, Accredited Practicing Dietitian
Hello, respectable and explanatory article. I wish to add a few notices. If you have high cholesterol, then you may inquire, will a low fat diet low down cholesterol? This is a important inquiry, because it is a best known fact that the most effective way to lower cholesterol is straightforward diet. Sure one element of a diet for lowering cholesterol will take on being low in fat. Merely this is unique part of the report. It is great to make that it is the concentrated fats that you want to eliminate it from the foods you eat.
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