Millions of overweight Americans consider food the enemy. And according to new research, this enemy plays devious mind games.

The same changes in brain chemistry that push drug users to snort cocaine or shoot up heroin may also drive overeaters to consume more calories than their bodies need. Gaining weight decreases the pleasure that we get from sugary and fatty foods. Eat a diet rich in these types of food, and one day you might need two pieces of cake to get the same enjoyment once provided by a single piece.