The process seems simple and sensible:
- Weight loss leads to improved physical health and a sense of accomplishment.
- Improved physical health and a sense of accomplishment lead to improved mental health
- Improved mental health leads to a brighter outlook on life.
The four-word summation of this process looks like this: Lose weight, feel better!
There’s only one problem with this common-sense view of weight loss. It might not be right.
Researchers Raise Doubts
On August 6, 2014, the website PLOS One published a peer-reviewed study that cast doubt on the common belief that weight loss success leads to psychological benefits such as reduced levels of depression.
The study, which was conducted in England, evaluated the physical and mental well-being of almost 2,000 individuals aged 50 and above. The data that was studied had been collected over a four-year period as part of the English Longitudinal Study of Ageing (ELSA).
The authors of the study (Sarah E. Jackson, Andrew Steptoe, Rebecca J. Beeken, Mika Kivimaki, Jane Wardle) described their objective in the following words:
The aim of this study was … to examine associations between changes in weight and changes in mood and wellbeing in a population sample of overweight and obese adults free from depression and serious illness at baseline. Cardio-metabolic changes were also examined to determine that participants were deriving typical benefits from weight loss and to facilitate comparisons with the trial literature.
All analyses were repeated adjusting for changes in health status and major life events that occurred over the weight loss period in order to test for confounding.
How the Study Was Conducted
The researchers divided study participants into three groups, based upon their weight loss or gain during the four years covered by the data collection:
- Those who had lost 5 percent or more of their starting weight
- Those who had gained 5 percent or more of their body weight
- Those whose weight remained within a 5 percent increase or decrease
Logistic regression examined changes in the following categories (controlling for demographic variables, weight loss intention, and baseline characteristics):
- Depressed mood (eight-item Center for Epidemiologic Studies Depression score ≥4)
- Low wellbeing (Satisfaction With Life Scale score <20)
- Hypertension (systolic blood pressure ≥140 mmHg or anti-hypertensives)
- High triglycerides (≥1.7 mmol/l)
Results of the Weight Loss Study
According to both the PLOS report and a press release on the ScienceDaily website, the results of the study showed a positive correlation between physical health and weight loss, but a negative correlation between mental health and weight loss:
- Before adjusting for serious health issues and major life events such as bereavement, which can cause both weight loss and depressed mood, the people who lost weight were 78% more likely to report depressed mood.
- After controlling for these, the increased odds of depressed mood remained significant at 52%
- The proportion of participants with depressed mood increased more in the weight loss than weight stable or weight gain groups (+289%, +86%, +62% respectively; odds ratio [OR] for weight loss vs. weight stable = 1.78 [95% CI 1.29–2.47]).
- The proportion with low wellbeing also increased more in the weight loss group (+31%, +22%, −4%), but the difference was not statistically significant (OR = 1.16 [0.81–1.66]).
- Hypertension and high triglyceride prevalence decreased in weight losers and increased in weight gainers (−28%, 4%, +18%; OR = 0.61 [0.45–0.83]; −47%, −13%, +5%; OR = 0.41 [0.28–0.60]).
- All effects persisted in analyses adjusting for illness and life stress during the weight loss period.
In an August 7, 2014 post on the New York Magazine’s “Science of Us” blog, Melissa Dahl noted that the mental health challenges related to weight loss may be a result of both frustration with setbacks and unrealistic expectations of the entire experience.
“It’s incredibly hard to keep weight off, requiring sustained use of self-control, something some research has suggested is a finite resource,” Dahl wrote. “So frustration from lack of willpower could be behind the drop in mood, the study authors suggest … [Also], a big change in your body doesn’t necessarily mean a big change in your life, and high expectations for a brand-new life to accompany your newly slim body can surely lead to disappointment. “
Conclusions and Analysis
In a press release that announced the publication of the study, the authors emphasized that their findings do not establish a connection between weight loss and depression:
It’s important to note this new result does not mean that weight loss necessarily causes depression directly, as depression and weight loss may share a common cause. However, it shows that weight loss outside the clinical trial setting cannot be assumed to improve mood and raises questions about the psychological impact of weight loss.
As study author Sarah E. Jackson noted, the results in no way diminish the benefits of achieving and maintaining healthy weight. They do, though, call attention to how both clients and professionals view the weight loss experience.
“We do not want to discourage anyone from trying to lose weight, which has tremendous physical benefits, Dr. Jackson said. “But people should not expect weight loss to instantly improve all aspects of life.”
One of the keys, Dr. Jackson said, is to approach weight loss with a clear understanding of the effort and well managed expectations for maintaining that weight over the long term.
“Advertising by diet brands may give people unrealistic expectations about weight loss,” she said. “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.”