Lipoprotein changes when a reported diet is tested in distance runners.

Diet records previously recorded by distance runners indicated that runners consumed considerably more calories, largely as carbohydrates, than did inactive controls. We examined the effect of this reported diet on the serum lipids and lipoproteins of active men. Ten male runners ran 16 km daily and were provided defined diets containing 3587 +/- 233 kcal/day (mean +/- SD) and composed of 53% (486 +/- 31 g/day) carbohydrates, 15% (134 +/- 8 g/day) protein, and 32% (131 +/- 9 g/day) fat for 21 days. Serum samples were obtained before and during the diet period. Low-density lipoprotein cholesterol fell 5 +/- 12 mg/dl before (p = NS) and 15 +/- 13 mg/dl (p less than 0.01) during the diet. High-density lipoprotein (HDL) cholesterol did not change during the week before, but decreased 6 +/- 2 mg/dl (p less than 0.001) while subjects consumed the defined diet. This decrease was due to a 7 +/- 6 mg/dl (p less than 0.01) fall in HDL2 cholesterol (1.063 less than rho less than 1.125 g/ml). Alterations in HDL cholesterol were accompanied by reductions in apo A-1, the major HDL apoprotein. After 14 days on the defined diet no additional changes in serum lipids occurred. Lipoprotein changes of this magnitude were unexpected and suggest that the diet diaries used to design the defined diet were unreliable or that factors not accounted for in diet records had significant effects in these subjects.