284 Low-Fat or Low-Carb?

The debate between low-fat and low-carb diets continues, but low-carb keeps coming out on top. A study published just last week in the Annals of Internal Medicine adds more “weight” (if you’ll pardon the pun) to the low-carb side.

The randomized trial, funded by the National Institutes of Health, divided 148 men and women, with no history of cardiovascular disease, kidney disease or diabetes, into two groups. The low carb group ate less than 40g of carbs per day of carbohydrates; the low fat group had less than 30% of their total calories from fat. Sixty participants in the low-fat group and 59 in the low-carb group completed the 12 month study. Measurements were taken at 3, 6 and 12 months.

After one year the low carb group, on average compared with the low fat group:
• lost 3.5 kg (nearly 8 lbs) more weight
• lost 1.5% more fat mass and gained 1.7% more lean mass
• had a lower ratio of total to HDL cholesterol (this is good)
• had a lower triglyceride level,
• had a greater increase HDL cholesterol (this is also good)
• had a decrease in C-reactive protein levels (a marker for inflammation)
• and, had a significantly lower risk score for coronary heart disease.

A similar trial published in Ann Intern Med in 2004 compared a low-carb ketogenic diet with a low-fat low-cholesterol reduced-calorie diet. The low-carb group lost twice as much weight, had a greater decrease in triglyceride levels, and greater increases in HDL levels. Significantly, only 50% of the weight lost by the low-fat low-calorie group was fat meaning that some muscle mass was burned. In the low-carb group 65% of the weight loss was fat suggesting that little muscle was lost. A weight loss with 75% fat loss is ideal with no muscle loss (the 25% non-fat loss is water and connective tissue associated with the fat cells). This trial however only lasted 24 weeks so the current study is much more significant.

These results should come as no surprise to anyone following the research on low carb diets. As I have explained in previous columns (#35, #65, #82), insulin is the key that prevents your body from burning fat, causing it to be stored in fat cells instead. An enzyme called lipoprotein lipase (LPL) is required to store fat, and insulin is necessary to switch LPL on. The carbs in a meal stimulate the production of insulin ensuring that the fat in that meal will be stored rather than burned. A high insulin level is also a factor in dyslipidemia (unhealthy cholesterol levels) (#83) and inflammation (#85).

After years of eating a high carb diet we can develop a condition called insulin resistance in which our insulin levels remain high no matter what we eat. This is a perfect situation for gaining fat weight, even on a calorie-reduced diet! A temporary ketogenic diet quickly clears insulin resistance and lowers the insulin levels to the point where body fat can begin to be burned.

For more information on this or other natural health topics, stop in and talk to Stan; for medical advice consult your licensed health practitioner.