Carbohydrate conservation in the obese: a theory to explain the ease of weight gain.

Changes in the blood concentrations of non-chylomicron triglycerides, insulin, glucose, non-esterified fatty acids (NEFA) and alanine in response to a 4.18-MJ (1,000-kcal) meal were measured in 15 obese and 15 lean volunteers. No differences between the two groups either in quantity or in the pattern of change were detected in the triglycerides, glucose or alanine during the 7-hour period of study. Insulin levels were significantly higher in the obese subjects 1.25 h after the start of the meal, but at no other time. Plasma NEFA were initially depressed in both groups, but thereafter rose to much higher levels in the lean subjects. The results support the hypothesis that the obese conserve more of their ingested carbohydrate as liver glycogen for use between meals, and thereby avoid the high energy cost of fat synthesis.