Researchers at the University of Cambridge have found that transitioning from school to work reduces physical activity, while motherhood accelerates weight gain, based on two comprehensive reviews.
As people move from adolescence into adulthood, weight gain becomes common, with obesity rates rising most sharply during this period. These changes stem from shifts in diet and activity tied to major life events, such as advancing from school to higher education or employment, forming new relationships, and starting families.
Experts from the Centre for Diet and Activity Research (CEDAR) at the University of Cambridge analyzed this in Obesity Reviews. They performed systematic reviews and meta-analyses of existing studies, synthesizing data from diverse research to draw reliable conclusions on exercise, diet, and body weight changes.
Leaving school
The first study examined the shift from high school to higher education or work among 15- to 35-year-olds. Reviewing 19 studies—17 on physical activity, three on body weight, and five on diet—researchers found that leaving high school correlates with a seven-minute daily drop in moderate-to-vigorous physical activity. Men experienced a steeper decline (16.4 minutes/day) than women (6.7 minutes/day). The effect was most pronounced when entering university, averaging an 11.4-minute daily reduction.
Three studies noted weight gain after leaving high school, though data was insufficient for precise averages. Two indicated poorer diet quality post-high school, and one after university.
Aging and parenthood
The second study assessed aging's impact, including parenthood. A meta-analysis of six studies showed mothers gained 17% more BMI than childless women over five to six years. For an average-height woman (164 cm), this meant about 7.5 kg gain for childless women (BMI increase of 2.8) versus an additional 1.3 kg for mothers (BMI 3.3).
One study on fathers found no significant difference. Evidence on physical activity was limited but suggested greater declines among parents. Diet changes showed no clear parental differences.
“BMI rises in women during young adulthood, especially mothers. Yet new parents may be motivated to change behaviors, benefiting their children’s health too,” said Dr. Kirsten Corder from CEDAR and the MRC Epidemiology Unit.
