The lifestyle a person shares with a partner has a greater influence than upbringing does on the chances of becoming obese, research suggests.
By middle age, the choices made by couples - including those linked to diet and exercise - will have a much greater impact than the lifestyle they shared with their siblings and parents when growing up, the study found.
The results suggest that people from families with a history of obesity can still reduce their risk by changing their habits.
Researchers said the study will help scientists better understand the links between obesity, genetics and lifestyle.
They said the findings reinforce the message that lifestyle changes in adulthood can have a significant impact in tackling obesity, regardless of a person's genetic profile.