Low carbohydrate diets may provide the best weight loss long-term without the hassle of calorie counting, a recent study has proven.  Studies on the effectiveness of different diets for weight loss have consistently shown equal or better weight loss with a low carbohydrate diet compared with a low fat diet, however long-term data was lacking.

A two year study just published in the July edition of the New England Journal of Medicine aimed to remedy this.  Researchers took a group of 40 to 65 year olds, who met the critieria of being either overweight, obese, diabetic or suffering from coronary heart disease.  Subjects were randomised to one of three diet groups.  The diets were structured to promote weight loss for the first six months followed by weight maintenance for the following 18 months.

• the low fat diet was calorie controlled, with 30% of calories from fat (including not more than 10% from saturated fat), with cholesterol limited to 300 mg per day.  Low fat grains, vegetables, fruits & legumes were emphasised.
• The Mediterranean diet group was also calorie controlled, with fat calculated to remain at less than 35% of caloric intake.  Poultry, fish & vegetables were emphasised, with daily consumption of olive oil & nuts recommended.
• The low carbohydrate diet did not restrict calories or fat intake, instead focusing on the restriction of carbohydrate intake to 20 g/day for the first two months, increasing to a maximum of 120 g/day after the weight loss period to maintain weight loss.  Vegetarian sources of fat & protein & avoidance of trans fats was promoted.

Around 85% of participants maintained dietary compliance for the two year period.  At follow-up, all groups had maintained a weight loss, with the averages for the groups; low fat - 3.3 kg, Mediterranean - 4.6 kg, & low carbohydrate - 5.5 kg.

In other metabolic markers, HDL cholesterol increased in all groups, with the greatest (0.22 mmol/L) increase in the low carbohydrate group.  LDL cholesterol did not change significantly in any groups.  The inflammatory marker hsCRP decreased significantly in both the low carbohydrate & Miditerranean groups, by 21 to 29%.  Fasting glucose & markers of insulin sensitivity were most improved in the Mediterranean diet group.  In participants with diabetes, glycated haemoglobin decreased significantly only in the low carbohydrate group.

Comment

Most studies of low carbohydrate diets consistenly demonstrate greater fat loss & better retention of muscle mass during weight loss.  A predictable effect on the lipid profile is also seen, with improvements in the typical insulin -resistant dyslipidaemia of high triglycerides, low HDL, & smaller, denser LDL particles.  These reproducible benefits make low carbohydrate diets the diet of choice for weight loss in most overweight individuals, especially those with insulin resistance.  The reduction in inflammation, as measured by hsCRP, is a very valuable additional benefit, especially for those at cardiovascular risk.  The authors noted that a particular benefit of the low carbohydrate diet was the achievement of superior wieight loss inthe absence of caloric restriction, thus being suitable for those experiencing difficulty following a calorie restricted diet.

KetoSlim System & support

Shai letal. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. Ne Engl J Med. 2008 Jul 17;359(3):229-41