To lose weight is to become happier. At least, this is the narrative voiced by countless health gurus, ubiquitous advertisements, and, sometimes, overly blunt friends and relatives.

Americans buy in to the weight-loss game with billions of dollars a year—money funneled into diet programs, gym subscriptions, and unscrupulously marketed miracle pills. On network TV, the long-enduring reality show The Biggest Loser, in which overweight men and women compete to lose the highest percentage of their total weight, is now on its 16th season. And personal tales of dramatic weight loss have long captivated the public, from Subway's Jared to Marvel leading man Chris Pratt, who lost 60 pounds for his role in last summer’s Guardians of the Galaxy.

The media tends to rally around these success stories, not only those who manage to lose weight, but also those who keep their pounds off. And it comes from physicians and friends as well. When I lost more than 60 pounds between high school and college, I got a taste of these accolades myself, from acquaintances, doctors, and romantic partners.

The presumption is that congratulations are due when people slim down—their weight loss has surely made them happier, right?

Even among academic researchers who study weight, obesity, and nutrition, that is a question that's been looked at infrequently. "I agree that this is an understudied issue," says James O. Hill, the executive director of the University of Colorado's Anschutz Health and Wellness Center and the co-founder of the National Weight-Control Registry (NWCR). Established in 1994, the registry has served as one of the largest fonts of information about successful weight losers, continually recruiting individuals who are at least 18 years old and have lost at least 30 pounds and kept them off for more than a year. Once enrolled, members are given extensive questionnaires and annual follow-up surveys on their weight-loss strategies as well as behavioral and eating habits.

Much of the work conducted by obesity researchers has centered around the intricacies of how and why people become obese and overweight, how and if excess weight is detrimental to health, and how to lose it. But there has also been a little exploration into how weight loss could affect the mind.

An extensive 2011 review of different weight-loss methods by Anthony Fabricatore, an assistant professor of psychology at the Perelman School of Medicine at the University of Pennsylvania, and others found that obese people generally experienced decreased symptoms of depression after taking part in a weight-loss trial. As noted in the review, that conclusion provides a sharp contrast to studies conducted throughout the 1950s. In a 1957 paper, AJ Stunkard—an eventual pioneer of obesity research—wrote that "for a large number of overweight persons, the current prescription of reducing diets has had unfortunate consequences; for a smaller number, it has been disastrous." These consequences included depression, anxiety, and even psychosis.

It appears that over the years, though, these obesity-treatment programs adopted a more balanced approach to weight loss. In a 2014 study examining the Look AHEAD project—an eight-year-long randomized, controlled trial of intentional weight-loss interventions, including diet and exercise, aimed at obese individuals with type-2 diabetes—the researchers concluded that the incidence of depressive symptoms were significantly lower among the treatment group than in the control.

But most people who try to lose weight are not surrounded by a team of health professionals. And the few attempts to look at a more representative slice of weight losers have presented some very counterintuitive findings.

Last August, a team of researchers delved into the English Longitudinal Study of Ageing (ELSA), a U.K.-based dataset keeping track of people 50 years old and above, updated every two years. The team was following up on earlier population studies that had found a negative association between weight loss and depressed mood. Though they were intrigued by the results, they also felt that these studies had too broad a focus, having included people who were at an ideal weight to start with and whose subsequent weight loss might indicate underlying health issues.

"We thought that if we excluded healthy-weight individuals from our sample, which previous studies showing adverse consequences of weight loss had failed to do, we would see positive changes in mood with weight loss that mirrored findings from the clinical-trial literature," the lead author, Sarah Jackson of University College London, says. "However, this was not the case; even when we restricted our sample to individuals who were overweight or obese, and [who] would therefore be recommended to lose weight, participants who lost at least 5 percent of their body weight were significantly worse off psychologically at our follow-up assessment than those who maintained their weight."

More specifically, they narrowed down the original ELSA sample to 1,979 overweight or obese individuals who reported no long-standing illness or clinical depression at the start of the study. The researchers then plotted out changes in measured levels of depressed mood, psychological well-being, hypertension, and triglycerides over a four-year period (the latter two factors known to be strong indicators of cardiovascular health). Even as their hypertension and triglyceride levels decreased compared to weight maintainers and gainers, weight losers were more likely to be depressed. Equally jarring was the finding that the weight-loss group saw no improvement in psychological well-being compared to the other two, though all three groups reported a higher level of depressed mood and a lower level of well-being over the four year period.

These longitudinal studies carry their own caveats—a direct relationship between cause and effect can be difficult to spot. Did weight loss influence people’s mood or the other way around? Maybe there was a chronic illness or particularly stressful life change that led to both a depressed mood and reduced appetite. Though Jackson and her colleagues attempted to control for pre-existing health conditions and life changes such as the death of a parent, those possibilities remain. What about the age factor? "It’s hard to know how well our results would extrapolate to younger age groups, but we would speculate that there would be a similar effect on mood," Jackson says.

If valid and reproducible however, their results bring up the likelihood that weight loss in and of itself doesn't come with the fanfare often expected of it. And if weight loss isn’t making people happy, that could explain, at least in part, why many people struggle to keep weight off.  "This could definitely contribute to the notoriously poor success people have with maintaining their new lower body weight after achieving significant weight loss," Jackson says. "If people do not find the benefits of being slimmer outweigh the costs involved in maintaining this, then they may slip back into old ways."

Hill is somewhat more circumspect about Jackson’s study. "The impact on both physical and mental health may depend on amount of weight loss," Hill says. "While I believe that 5 percent weight loss can make a positive impact on health, I’m not sure it has a big impact on the mental side of things. This may take much more weight loss."

Hill and his colleagues have taken an indirect look at this question themselves, concluding in a 1998 study of the NWCR that long-term weight loss was not associated with psychological distress. While the registry is certainly useful, it's hard to generalize its conclusions to the greater population, since its participants are self-selected and the measurements rely on self-report. (Those happier with their weight loss might be more likely to enroll in the registry to begin with, and while the NWCR does ask for documentation of a participant’s weight loss, it’s an optional step). Still, even Hill notes that, "not all reduced obese are the same and some are not happy with their weight loss." In another analysis of the NWCR in 2012, the authors described four different groups of people with different attitudes toward their weight loss, finding that 26.6 percent of NWCR participants struggled with maintaining their weight, were less satisfied with their weight loss, and less able to cope with stress.

Thinking back to my own painful days of 10-mile runs five times a week, it's hardly news to me that a weight-loss regimen comes with significant challenges and mental strains. Without the benefit of a fitness coach or dietician, I suffered through injuries and fatigue as I lost weight, all the while isolating myself from friends and family. My running routine and calorie-watching bordered on obsessive and unhealthy. And even once I had dropped down to 160 lbs, from a maximum of 226 lbs, my throat clenched with dread and worry if the number on the scale rose by a pound or two. Yet people I knew saw me as an inspiration, an uplifting example of willpower.

It’s not just about willpower, though. Obesity researchers understand that there are significant environmental and biological obstacles to long-term weight loss. A recent paper in The Lancet concludes: "Changes in brain chemistry, metabolism, and hunger and satiety hormones, which occur during attempts to lose weight, make it difficult to definitively lose weight."

For instance, the Look AHEAD study did indeed find that the group given intensive weight loss interventions was able to lose and keep more weight off than those simply given the standard treatment for diabetes, but they had on average lost only 4.7 percent of their initial body weight after eight years, a measly improvement of 2.6 percent over the control group. (There were numerous health improvements unrelated to weight loss in both groups though.)

It's difficult to reconcile this knowledge with the ongoing efforts to promote long-term weight loss as a primary means of battling the surge in chronic illnesses like diabetes and heart disease.

And the cultural imperative to equate thinness with healthiness, and with happiness, might leave people disillusioned with their progress.

A growing body of research shows that just being active might be more important than losing weight. In 2013, a meta-analysis looking at the relationship between fitness and weight on overall mortality rates found that overweight and obese individuals who had strong levels of cardiorespiratory fitness, a measure known to predict habitual physical activity, suffered no greater mortality risk than those at a so-called “normal” weight who were also fit.  It was lack of fitness, not body mass index, that predicted an earlier death. The researchers concluded that health professionals would be better served to "focus on physical activity and fitness-based interventions rather than weight-loss driven approaches to reduce mortality risk."

Another finding of Fabricatore’s meta-analysis provides further evidence against the idea that losing weight will lighten people’s emotional burdens: While extensive lifestyle modifications in dieting and exercise produced the greatest improvement in symptoms of depression, there was absolutely no correlation between an improved mood and weight lost. In fact, nearly all the interventions, including those that didn't focus on weight loss, had a similar effect. "Thus, other elements of treatment were likely responsible for the favorable effect on mood," they concluded. It seems to have been the healthy lifestyle changes and supportive environment that improved people’s spirits, not shedding pounds.

And while Jackson doesn't want her study to discourage people from attempting to lose weight, it appears that the greater lesson to take away from her and others’ research is that weight loss alone isn’t a prescription for happiness. When people struggle for thinness, they can sometimes emerge the unhappier for it, and often just see the weight come back. Perhaps it’s better to promote a long jog and good eating habits for the sake of health alone.

It's been eight years since I first started running and I can safely say that I'm as happy as ever. But I'm also about 15 pounds heavier than I was at my lightest. I still jog twice a week, keep tabs on my eating habits and try to be comfortable with my body, the stretch marks and sagging skin underneath my shirt another unspoken consequence of large weight loss. I lost 60 pounds once, but in that same time I’ve also performed Off-Broadway, watched my nephew take his first steps, and eaten coconut ice cream at 2 o'clock in the morning. And, unlike the numbers on a bathroom scale, the happiness those experiences have brought me is unquantifiable.