The study featured six women and seven men, all of whom were obese, who went on a low-carb diet for two weeks. The subjects ate anything they wanted, as long as the total carbs didn’t exceed 20 grams, and they did aerobic exercise at an intensity level equal to 65 percent of maximum oxygen intake, a relatively low intensity that favors fat burning, especially in out-of-shape people.
The researchers measured fat and protein burned by the subjects both at rest and during exercise. The subjects stopped burning carbs at rest and burned 25 percent fewer carbs after 15 minutes of exercise. Protein oxidation increased by 38 percent at rest, remaining elevated during exercise. Fat oxidation increased slightly at rest, but it increased 50 percent during exercise in response to the diet. The subjects also reduced their total calories while on the diet. The men lost some lean mass, while the female subjects did not; however, the lean mass lost by the men wasn’t muscle but glycogen and water.
This study points to two essential features of low-carb dieting. First, the lack of carbs does increase protein oxidation, thus requiring a greater-than-usual protein intake, perhaps at least one gram per pound of goal weight. The other point is that you burn far more fat while working out during a low-carb diet.
In another study presented at the same meeting, researchers determined the effects of a ketogenic, or low-carb, diet on blood lipids. They wanted to evaluate how low-carb dieting affected small dense low-density-lipoprotein cholesterol. That type of LDL cholesterol is considered the most dangerous in terms of cardiovascular disease onset. People having this LDL profile, known as pattern B, have a three times greater incidence of coronary disease than those who don’t.
The study involved 25 men who were on a ketogenic diet for six weeks. At the end of that time their blood triglycerides, or fat, had decreased by 39 percent. Meal-related elevations in blood fats had dropped by 33 percent, insulin by 40 percent and bodyfat by 11 percent. Peak LDL diameter increased by 1.8 percent, pointing to a beneficial change in the size of LDL particles. Most of the benefit of the ketogenic diet in relation to cardiovascular disease was attributed to a greater clearance of triglyceride in the blood following a meal. Higher postmeal fat levels in the blood favor smaller, denser, more dangerous LDL.
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
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