Rats were fed either normal or subnormal amounts of a 60% carbohydrate (sucrose) diet for 12–14 days. Food was available to the control animals at all times and was presented to the undernourished rats either all at once, under which conditions it was eaten in 1–2 hours, or hourly in 24 small aliquots. When lipogenesis by epididymal fat pads of the animals was evaluated, by measuring acetate-1-14C incorporation into lipid in vitro, it was found, compared with the controls, that (a) the rats eating the limited amount of food in a short time period demonstrated increased lipogenesis and (b) those eating 1/24 of the restricted diet every hour exhibited decreased fat formation. It is concluded that when measuring the dynamics of intermediary metabolism, both the amount and the timing of food ingestion require strict control.