A low-fat high-carbohydrate diet raises blood fats, unless it is combined with moderate exercise.
It's assumed that a low-fat diet will reduce heart disease risk by lowering levels of cholesterol, especially low-density lipoprotein (LDL or 'bad' cholesterol). But a low-fat diet is often a high-carbohydrate diet (because you have to get calories from somewhere). And it's becoming evident that a high-carbohydrate diet raises levels of triglycerides, blood fats also linked to heart disease risk.
But researchers at Loughborough University, England, have found that the drawbacks of a high-carbohydrate diet can be modified by exercise. They tested eight women in their 50s and 60s, and gave them a series of three day diets: low-carbohydrate, high-carbohydrate without exercise and high-carbohydrate with an hour of brisk walking a day. At the end of each diet, triglycerides were measured. As expected, triglycerides were higher after high-carbohydrate diet without exercise than after the low-carbohydrate diet. But the increase in triglycerides was significantly lower after the high-carbohydrate diet plus exercise than this diet without exercise.