It has been commonly reported that married couples tend to gain weight, while a divorce can provoke weight loss. However, for the first time, researchers have found a link between weight gain and connubial bliss. The study found that the happier that a person is in their marriage, the more weight that they tend to gain.

The researchers recruited 169 young couples who had all been married for fewer than six months and tracked them over the course of four years. The grooms were an average age of 25 years old and, with an average body mass index (BMI) of 26, were generally overweight. The brides were an average age of 23 years old and, with an average BMI of 20, were within the normal range. Over the course of the four years, the couples met with the researchers eight times in order to assess if they had gained any weight and how happy they were with their pairing.

The researchers found that, even after compensating for pregnancy and other obvious factors, married couples who were happier tended to gain more weight. Unhappily married couples tended to gain less weight. The researchers believe that this association exists because happily married couples feel like their years of dating or over, meaning that they no longer need to maintain a healthy weight. On the other hand, unhappily married couples may be considering divorce, causing them to maintain a healthy weight. Lead researcher Andrea Meltzer, a professor at Southern Methodist University, described this concept to HealthDay as the "mating market" model.

For each unit of increase in satisfaction found, either by the person or the partner, a 0.12 increase in BMI occurred every six months, on average," Meltzer explained.

Therefore, a woman who weighs 140 pounds and is 5-foot-4 inches would have a BMI of 20.6. An increase of a half-pound would raise her BMI by 20.7. By the end of four years, she would still be classified as healthy, but researchers note that they have not explored findings beyond four years.

However, Charlotte Markey, an associate professor at Rutgers University, New Brunswick, said that other explanations may exist for the finding. She suggested that happily married couples may eat more often together, and eating with other people may cause people to eat greater quantities of food.

Meltzer presented her findings at the annual meeting of the Society for Personality and Social Psychology in New Orleans.