Gaining and Losing Weight at the Same Time

While it’s true that genetics plays a role in determining body weight, so does living together. Although spouses do not share a gene pool, they do share an environment. And there’s a considerable amount of research showing that people who live together, particularly spouses, tend to have similar BMIs. And if that shared environment is encour- aging weight gain, there may be an increased risk of obesity. In a study of the relationship between marriage and the development of obesity, researchers followed newly married spouses for two years.
At the end of the study, they found that the couples had similar BMIs and that marriage was associated with weight gain. It also appeared that the couples’lifestyle involved eating calorie-laden foods and not engaging in physical activity—and that their newly acquired living arrangement was at least partially to blame for the weight gain.

Why does living together predispose partners to weight gain? The answers fall into two categories. First, marriage generally increases eat- ing opportunities because married people tend to eat together, rein- forcing a habit of eating more often. For example, a single woman living on her own may opt for a simple salad for dinner after a busy day at work. Once married and preparing a dinner that she and her hus- band will share, the woman is more likely to prepare and eat a more complete—and higher-calorie—meal. In addition to having more opportunities to eat with someone, the newly married person may have less motivation to stay thin. In a single world, both men and women want to maximize their attractiveness to the opposite sex, and for many that includes having a trim figure. With marriage, the com- fort of being in a stable relationship can lead to a reduced commitment to maintaining one’s weight.