Figure 1.

Fructose alters weight regulation. Under normal conditions, most animals tightly regulate their weight. If they are fed a hypercaloric diet they will gain weight, and if they are given a hypocaloric diet they will lose weight, but then they will spontaneously correct to their normal weight when they are allowed to resume their normal diet. By contrast, fructose acts by reducing intracellular ATP while at the same time blocking the replenishment of ATP from fat stores. Over a period of days to weeks, the animals develop leptin resistance, resulting in increased energy intake. However, ATP production stays low due to suppression from oxidative stress. As a consequence, the calories that are ingested are preferentially routed to generate fat. Over time ATP levels are repleted, but at the expense of a dramatic increase in fat stores. (Online version in colour.)