Will Losing Weight Really Make You Happy? New Study Says Probably Not

Although physical health is significantly improved by weight loss, the effects of losing weight on mental health are less clear, according to new research from the University College London in the UK. In the study, researchers found that losing weight may actually increase the risk of adverse psychological conditions. However, as the effects are not causal, these findings must be interpreted carefully. 

With the global obesity epidemic growing at an alarming pace, many public health organizations have taken to recommending weight loss as a health promoting behavior. The physical health benefits of weight loss are overwhelming: Even small reductions in body weight are associated with a significantly reduced risk of chronic conditions including diabetes, heart disease, arthritis, and stroke.

However, the evidence regarding the psychological benefits of losing weight remains inconclusive. Clinical trials of weight loss have been shown to improve participants’ mood, but many believe these apparent benefits are the result of the supportive environment rather than the weight loss itself, particularly as the effects are seen very early on in treatment and are not related to the extent of weight loss. Furthermore, these benefits are not found in population-based research — in fact, some studies even suggest that weight loss could increase the risk of negative psychological outcomes.

In the new study, researchers examined 1,979 overweight or obese individuals in the U.K. to investigate the effects of weight loss on both physical and mental health. During a four-year period, the team monitored participants’ body weight, blood pressure, cholesterol, and general health status. They also asked participants to complete surveys assessing their overall mood. Questions covered how sad, lonely, motivated and sleep-deprived they had felt in previous weeks.

‘Be prepared for the challenges’

Overall, 14 percent of the participants lost at least 5 percent of their body weight – the mean weight loss was 6.8 kg (15 lbs) per person. Seventy-one percent of participants stayed within 5 percent of their original weight, while 15 percent gained at least 5 percent of their initial body weight (the average weight gain was 6.4 kg, or 14.1 lbs).

Unsurprisingly, losing weight led to significant physical benefits: those in the study who lost 5 percent or more of their original body weight over four years exhibited a drop in blood pressure and reduced serum triglycerides, both of which lower the risk of heart disease.

In an interesting pattern, all participants — regardless of their weight-change status — deteriorated psychologically over the four-year period. However, after controlling for health issues and major life events that could cause depression, participants who lost weight were 52 percent more likely to report a depressed mood than those who stayed within 5 percent of their original weight:

Though the study doesn’t show that dieting causes depression, it does demonstrate that weight loss doesn’t necessarily improve mental health, as many people assume. In fact, the depressive symptoms could stem from disappointment after losing weight fails to result in significant changes. When we imagine ourselves losing weight, we tend to picture ourselves as magically richer, more confident, and generally living a better life alongside dropping a few sizes. When we see that weight loss doesn’t change everything, it can be a bit of a letdown.

“We do not want to discourage anyone from trying to lose weight, which has tremendous physical benefits, but people should not expect weight loss to instantly improve all aspects of life,” said lead author Sarah Jackson. “Aspirational advertising by diet brands may give people unrealistic expectations about weight loss. They often promise instant life improvements, which may not be borne out in reality for many people. People should be realistic about weight loss and be prepared for the challenges.”

But Jackson points out that this negative effect on mental health could be more a function of the stress of dieting, rather than a consequence of the actual weight loss. “Resisting the ever-present temptations of unhealthy food in modern society takes a mental toll, as it requires considerable willpower and may involve missing out on some enjoyable activities. Anyone who has ever been on a diet would understand how this could affect wellbeing,” she said. “However, mood may improve once target weight is reached and the focus is on weight maintenance. Our data only covered a four year period so it would be interesting to see how mood changes once people settle into their lower weight.”

She also says that health care professionals should monitor both the physical and mental health of patients when recommending weight loss and offer ongoing support as needed.