Weight loss towards adulthood reduced the risk of depression later in life

A new large-scale study has found that while above-average height in childhood is associated with an increased risk for mental health, normal weight to maturity appears to address this vulnerability.

Obesity and mental disorders are two serious health problems, the interrelationship of which includes biological and social components. The fact is that adipose tissue secretes inflammation molecules that affect neurotransmitters, and people with obesity face stigma.

A group of researchers from the Chinese Medical University, led by Dong-Rong Li and Qi-Jun Wu, wanted to find out whether the risks associated with being overweight in childhood are permanent or can be changed. They analyzed data from 368,756 participants in the UK Biobank aged 40-69, excluding those who already had depression or anxiety. Participants reported what their body size was at 10 years old (thin, medium, full), and the researchers measured their current BMI. Over the 13 years of follow-up, there were 11,546 new cases of depression and 15,780 cases of anxiety.

Any deviation from the average in childhood was associated with an increased risk: those who remembered being thinner had a 9 percent higher risk of depression and a 13 percent higher risk of anxiety. Adult weight showed a stronger association: the lowest risk of depression was at a BMI of 23–24; overweight had an 18 percent higher risk of depression, 52 percent higher risk of obesity, and 15 percent higher risk of anxiety.

When comparing weight trajectories, those who lost weight as a child and became obese as adults were most at risk. Full in childhood but thin enough in adulthood showed no significant increase: their risks were comparable to those who were average in childhood and normal adults. This suggests that the psychological risks associated with childhood weight are potentially reversible.

The study draws on memories of body size at 10 years old, which may be imperfect and categories subjective. As an observation, it does not prove causality. For example, other factors can affect both weight and mental health. In addition, the biobank mainly consists of volunteers of European descent. Future work could include genetic data or repeated weight measurements throughout life.