Biological changes associated with puberty may influence the development of binge eating and related eating disorders, according to a study on female rats conducted by the National Institute of Mental Health (NIMH)-funded researchers. After puberty, the rats showed binge eating patterns that resemble those in humans, supporting the role of biological factors, since rats do not experience pressures to be thin or other psychosocial risk factors commonly associated with human eating disorders.
Among girls, symptoms of binge eating or bulimia nervosa often arise around puberty. Past research has largely focused on psychosocial roots for this association, but biological changes that occur during and after puberty are likely to have an effect as well. Kelly Klump, Ph.D., of Michigan State University, and colleagues tested this theory in an animal model since animals do not experience psychological risk factors during puberty. They used a rat model that can distinguish between rats that are resistant to binge eating (BER) from those prone to binge eating (BEP), based on their individual eating habits. For this study, the researchers studied binge eating risk from pre-puberty to adulthood in 66 female rats. In addition to their standard food, the rats were provided intermittent access to cake frosting, a highly enjoyable but nutritionally empty and high fat food.
Over the course of development, all rats ate more frosting as they matured. However, a difference in frosting intake between BER and BEP rats emerged during puberty; no differences in frosting intake were observed in pre-puberty, but large differences were observed in puberty and adulthood. The researchers noted that rats in the BER and BEP groups ate similar amounts of the standard food and were similar in body weight. This suggests that the BEP rats were not overeaters generally, but were instead, prone to binge eat on high-fat foods only.
The findings reveal dramatic increases in binge eating proneness during puberty, suggesting that increases in binge eating and similar eating disorders during and after puberty in girls may be partially due to biological factors. Similar to binge eating in humans, BEP rats ate much more of the high-fat food but did not increase their consumption of the standard food. Also, all rats preferred the high-fat food, regardless of developmental stage, which is similar to behaviors seen in girls; for example, girls tend to prefer candy over healthier treats at all ages. In both rats and humans, this behavior begins to diverge during puberty, with some consuming much more of the high-fat food than others. Unlike humans, however, the percentage of binge eating rats (30 percent) was much higher than estimates in humans (3.5–19 percent). According to the researchers, this difference may indicate that binge eating in rats is a “pure” form of binge eating that is unmodified by psychosocial factors, such as social disapproval or guilt that tends to decrease binge eating rates in humans.
More research is needed to develop and validate animal models of the cognitive and behavioral symptoms of eating disorders. Studies exploring the mechanisms underlying developmental changes that occur during puberty, for example the action of ovarian hormones, may also inform research on eating disorders.