New animal research helps explain why some eat without hunger or to excess. The studies explore the biological effects of poor eating habits, showing that high-fat diets cause lasting brain changes that may impair healthy eating. Additional studies show that food and drugs of abuse engage many of the same brain systems. The findings were presented at Neuroscience 2010, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news on brain science and health.

More than one billion adults worldwide are overweight, according to the World Health Organization. With increased risk for chronic disease and rising health care costs tied to obesity, today's studies are valuable in helping generate future prevention and treatment techniques.

Specifically, today's new findings show that:

* Animals fed a high-fat diet show long-term brain changes in the pleasure centers of the brain, illustrating the biological challenges for obese individuals (Teresa Reyes, PhD, abstract 299.18, see summary attached).

* The same substance may signal satiation and pleasure. The stomach hormone ghrelin, which normally indicates when an animal is hungry or full, fueled cravings for sugar that resemble those for drugs (Karolina Skibicka, PhD, abstract 191.6, see summary attached).

* A chemical released in the body during food restriction is a contributing factor in drug-seeking behavior. Research shows that drug-exposed rats are less likely to relapse when that chemical signal is blocked, suggesting a potentially novel treatment for recovering drug addicts (Uri Shalev, PhD, abstract 368.25, see summary attached).

* A sex difference may exist in addictive behavior. When given a choice between food and cocaine, male rats preferred sweets and female rats favored cocaine (Kerry Kerstetter, abstract 266.6, see summary attached).

Other recent findings discussed show that:

* A predisposition to obesity and food addiction might be hardwired at or around birth, and good nutrition in early life is essential for development of brain centers involved in regulating weight (Sebastien Bouret, PhD, see attached speaker's summary).

"Life experiences change the nervous system, and today's findings demonstrate why regulating food intake and body weight is such a challenge," said press conference moderator Ralph DiLeone, PhD, of Yale University School of Medicine, an expert on the neural mechanisms of food intake and behavior.