Recent dramatic increases in prevalence have made obesity the number one nutritional problem in the US. Of particular concern is the fact that, although available treatments are effective in producing clinically significant weight loss, their ability to sustain weight loss long term is poor. This study is based on a conceptual analysis of this problem that argues for greater attention to two issues related to the temporal dynamics of the challenge of long-term weight control. These are: 1) the environment is continually changing and is not supportive of weight control and 2) the intervention methods that are effective in inducing short-term changes in behaviors and weight often lose their potency over time because of habituation.