Lean and mean: it's all in the hormones

We all know that reducing your carbohydrate intake can result in rapid weight loss or more ripped, defined muscles, but the evidence to date has been largely anecdotal.

 

Some link the body fat change to the hormone insulin in response to carb consumption. However, many conservative dieticians and nutritionists are sceptical due to lack of scientific support, putting the results down to calorie restriction.

 

A recent study at the University of Connecticut, published in the Journal of Metabolism, July 2002, may give the unbelievers some food for thought.

 

Researchers tested the effects of a six-week carbohydrate-restricted diet on body composition in relation to hormone response.

 

Twelve healthy normal-weight men switched from their habitual diet (48% carbohydrate) to a carbohydrate-restricted diet (8% carbohydrate) for six weeks. Eight men served as controls, consuming their normal diet. The men were encouraged to consume adequate dietary energy to maintain body mass during the test. Total and regional body composition and fasting blood samples were assessed at weeks 0, 3, and 6 of the test period.

 

Fat mass in the carb-reduced group was significantly decreased (by an average of 3.4 kg) and lean body mass significantly increased (by 1.1 kg) at week six. The group had a significant decrease in serum insulin (34%), and an increase in total thyroxine (by 11%).

 

Researchers noted that about 70% of the change in fat loss on the carb-restricted diet was due to the decrease in serum insulin. There were no significant changes in glucagon, total or free testosterone, sex hormone binding globulin (SHBG), insulin-like growth factor-I (IGF-I) or cortisol uptake, nor were there significant changes in body composition or hormones in the control group.