Why Weight Loss Diets Fail
About 10 years ago, I decided I wanted to lose weight. A Google search told me that there were plenty of lose-weight-quick solutions to try: Low-carb, low-fat, vegan, and Paleo diets all were top contenders. At the time, I wasn’t really into critically evaluating what I was reading, so I decided that a low-carb diet was the right fit for me.
It worked. Over the next eight months, I lost about one third of my body weight. I have maintained that weight loss since, but it hasn't been easy. I have managed my weight using a seemingly never-ending succession of different high-maintenance diets (looking at you, keto), while secretly hoping all the while that I might one day find a diet that results in seamless, no- to low-effort weight maintenance. Of course, as anyone who’s ever tried to lose a lot of weight (and maintain that weight loss) knows, that diet basically doesn’t exist. Now that I’m older and have a lot more nutrition education under my belt, I have a lot more perspective and understanding about why.
The truth is, I stumbled into a weight-loss strategy that worked for me not because I found the magic diet, the one with the no-fail macronutrient ratio or the one that told me to avoid all the right foods, but because I—very much by accident—changed my entire lifestyle, and then stayed vigilant about it. The thing I didn’t know when I first set off on my weight-loss journey, that I now realize as I finish up my Ph.D. in nutritional sciences, is that traditional diets don't always work, at least not in the way that the Internet tells you they do, and that they can often fail, especially in the long-term. In the interest of helping past Kevin (and anyone like me) understand what he was getting himself into, let’s take a look at what we know—from large-scale studies conducted over long time periods—about how diets work and don’t work, and why.
Diets are nothing new. In fact, we've been fixated on restricting what's on our plates for hundreds of years, at least.
In the early to mid 1800’s, Sylvester Graham (of Graham cracker fame) popularized a strict form of vegetarianism that piggybacked on the temperance movement. Graham advocated for limiting consumption of meats, alcohol, and refined grains, not as a way to diminish our waistlines, but our libidos. Not unlike what we see with modern diet culture, the popularity of Graham’s diet soared and devotees, or “Grahamites,” provided enthusiastic testimonials. Outbreaks of communicable diseases, such as cholera, in the 19th century led to claims that the Graham diet helped to both prevent and treat infection. While Graham’s diet today wouldn’t likely take Instagram by storm (#grahamdiet), its popularity illustrates humanity’s deep want and love for a quick fix solution. Graham’s Spartan approach to food and alcohol intake is just one example in a long history of diets that promised be a cure-all for a ton of ailments, some societal, and bring overall health. Like the diet advocated by Horace Fletcher, an early 20th century version of an influencer who recommended chewing food until it turned to a near liquid in the mouth, promising that this would prevent overeating and promote health. Or, way before Graham and Fletcher, the second century Roman senator who advocated eating copious amounts of cabbage—and bathing in the urine of those who ate copious amounts of cabbage—which he believed would bring vim and vigor. Like I said, diets—and their fantastic promises—are nothing new.
But as times change, so also do the diets themselves, as well as what they promise to change, fix, or cure. Though few individuals nowadays would be interested in a diet because of its purported anti-cholera effects, diet fads continue to be extremely popular, with those that promise weight loss and metabolic health dominating the wellness landscape. The messaging about our waistlines is nearly ubiquitous, ranging from Oprah interrupting your show to tell you that she loves bread and eats it every day on her diet and still manages to lose weight, to Dr. Oz trumpeting the latest rapid fat-burning product on daytime TV. And on social media, celebrities and influencers endorse products like “flat tummy shakes” and "weight loss tea." Research suggests that more than 40 percent of adults worldwide in the general population have attempted to lose weight at some point.
This fixation on dieting isn’t terribly surprising, given the perceived impact of dieting on weight loss, and our society's near obsession with losing weight thanks to pervasive weight stigma and the conflation of weight loss, by any means, with health.
Research shows that even after losing weight, people often will struggle to keep that weight off.
Over the past several decades, researchers from a mix of backgrounds—nutrition, psychology, physiology among them—have tested a variety of different diets in short- and long-term settings. And while it’s easy to find individual trials to support a particular way of eating (which accounts for articles, blog posts, and books telling you that a particular diet has “been shown” to do a particular thing), a comprehensive look at the data actually does not support any one weight loss diet over another for the general population.
One large-scale study review found “minimal” difference between how much weight people lost on particular branded diets, even while concluding that dieting in general offers “considerable weight loss benefits." Perhaps not surprisingly, the authors note that “most calorie reducing diets result in clinically important weight loss as long as they are maintained.” In other words, exactly how you calorie reduce may not matter that much, but calorie reduction maintenance—keeping it up over time—probably does. The researchers end by recommending any diet a patient will adhere to. Which is kind of exactly the issue.
For most individuals, not only does weight loss slow down over time, it can also reverse; people who lose weight often gain it back. In 2005, an interdisciplinary group of researchers started a workplace-based study called the “Dietary Intervention-Randomized Controlled Trial” (DIRECT), in which 322 moderately obese adults over the age of 40 (the mean age was 52, and 86 percent were men) were randomly assigned to either low-fat/restricted calorie, low-carbohydrate/no calorie restrictions, or Mediterranean style/restricted-calorie diets, and met with registered dietitians for 18 90-minute sessions over two years. This trial has an added bonus: Participants received a four-year follow-up analysis after the two-year period ended, allowing researchers to also take a look at any long-term (six years total) effects of the diets. In their findings, published in 2008, they found that participants assigned to all three diets gained back lost weight. After six years, net weight losses (so, the weight they lost after accounting for what they gained back) were one pound, seven pounds, and four pounds for the low-fat, Mediterranean, and low-carb groups, respectively.
The DIRECT study is not an outlier in the weight-loss literature; researchers have observed weight regain following weight loss across a range of populations and types of weight loss diets. As early as 1993, the National Institutes of Health Technology Assessment Conference panel published a paper on methods to better enable long-term weight loss without substantial regain. The report noted that the evidence from weight loss trials showed that up to two-thirds of all weight lost through controlled weight loss programs is regained within a year, and within five years, almost all of it has been.
Recent studies have largely confirmed these early findings. In the 10-year follow up of the Diabetes Prevention Program, a massive study showing the potential for weight loss interventions to reduce cases of diabetes in high-risk adults, participants who had lost, on average, 15 pounds had, after one year in the program, regained about 10 pounds of the lost weight.
So why, exactly, is long-term weight loss so hard for so many people?
For one, our bodies are not wired to make weight-loss easy, particularly in the environment and under the circumstances in which we live.
In 2014, the National Institutes of Health convened a panel to discuss the state of the science on this exact issue—the problem of weight regain after weight loss—highlighting the biological, environmental, and behavioral factors that can make long-term weight loss so difficult. As the panel noted, following weight loss, a number of physiological adaptations occur to reduce the number of calories the body burns, which in turn requires people to cut even more calories in order to keep losing weight. But reducing calories becomes more and more challenging as the brain adapts to weight loss. Why? The brain’s response to caloric restriction tends to be to increase cravings for foods that are highly rewarding (delicious stuff that’s some combination of sweet, fatty, and salty) and reducing our perception of being full. In short, our body and our brain work together to vigorously defend against weight loss and promote weight regain. It’s an unending “feedback loop,” and once the loop gets off kilter, it’s very hard to turn it back around. As David Levitsky, Ph.D., professor at Cornell University’s School of Human Ecology, tells SELF, “The body has had millions of years to develop mechanisms to resist starvation. You cannot bypass them by simply going on a diet.”
There’s also the fact that most diets are structured with short-term, unsustainable goals in mind.
I reached out to Courtney Plush, R.D., who works with patients seeking surgical and nonsurgical weight management at the Emory Bariatric Center in Atlanta, Georgia. She explained some of the unique pitfalls of the “diet mentality.” She tells SELF that on one hand, weight-loss diets work (in theory) because if you create a set of rules that reduce calorie intake, you will likely lose weight while you follow those rules. But (in practice), diets tend not to work because most people embark on caloric restriction for a set period of time. Once the diet “ends,” they’re likely to regain the weight. Diets frequently fail because “...they have an endpoint and are not real lifestyle change,” Plush says. This sentiment is laid out thoroughly by the Academy of Nutrition in Dietetics in a 2013 position paper urging nutrition practitioners to focus on the "overall pattern of food eaten … on variety, moderation, and proportionality in the context of a healthy lifestyle, rather than targeting specific nutrients or foods."
Diets tend to approach nutrition and weight loss as a temporary state of mind, but maintaining a lifestyle that promotes a healthy weight and metabolism is often a lifelong journey. Of course, many of us wish that long-term weight loss was as simple as going on a low-carb diet for six weeks, but the research and patient experiences suggest that this approach is doomed to fail for most. Structured interviews with participants in weight loss trials describe diverse barriers to weight loss that the black-and-white, good-or-bad thinking about food encouraged by diets ultimately fails to address. Plush says that she wishes more research was available to tease out the impact of dieting on psychological stressors and its relationship to weight loss. “Many of my patients who have tried diets and been unsuccessful at maintaining weight loss feel guilty," she says. "Part of my job is teaching them that it is the diets that fail, not the individual."
Yoni Freedhoff, M.D., an obesity physician and founder and director of the Bariatric Medical Institute in Ottawa, Canada, suggested another reason why diets fail that isn’t considered often enough in the research. “I think most people, and many research protocols, encourage dieters to take on lifestyles that at best are tolerable, and at worst involve ongoing suffering by way of some combination of cultivating hunger or cravings, eliminating enjoyable foods or food groups, and making it difficult to lead normal lives with friends or family. So perhaps it's not surprising that the outcomes of diets that involve suffering are short lived," he tells SELF. Freedhoff also suggested that, in addition to pushing eating patterns that are unpleasant, diets, both in research and real-life settings, often encourage weight loss goals that are not in sync with reality.
As we’ve seen with our discussion of the weight loss literature, small amounts of weight loss are achievable, but rarely in line with the promises of our diet culture. Freedhoff uses the “best weight” approach with his patients, which is, rather than setting a goal weight, work towards the weight that is what you can achieve while living the healthiest lifestyle you can actually, truly enjoy.
Finally, we can't talk about weight regain without also talking about the psychological, social, and societal factors involved.
An emerging body of research has begun to highlight the negative impact that weight stigma and discrimination has on weight loss. People who experience bias because of their weight may be at an increased risk for developing obesity and staying obese. In other words, shaming people into losing weight doesn't work. Instead, it further perpetuates weight stigma, mistreatment of people with bigger bodies, and psychological harm.
There are also features of our food environments that can hinder weight loss efforts. One major defining factor is the availability of hyperpalatable foods—foods that are calorie-dense, low in nutrients, and are manufactured to be incredibly pleasing to eat (thanks to carefully engineered flavor, texture, and consistency)—which often have been engineered to be overeaten. Coupled with large portion sizes, the ubiquity of food ads, and other food- and eating-related external cues, our environment is influencing the amount that we eat and helping to stack the deck against long-term weight loss and ultimately helping facilitate weight regain.
Kevin of 10 years ago might read this article and say, “Kevin, you’re a hypocrite. You went on a diet and lost weight. Diets work.”
My past self, however, would be wrong, or at least not understanding the big picture fully.
Look, this research isn't saying that losing weight or keeping it off is impossible; a lot of people know someone who has lost weight and maintained their weight loss for years. But for many, maintaining a traditional weight-loss diet of caloric or food-group restriction is a serious challenge, and doesn’t have a high chance of producing substantial or sustainable weight loss. In fact, a history of dieting can be associated with greater weight gain, not weight loss. Promises made by trendy diets, shakes, and supplements don’t appear to live up to their assertions or hype. And that's to say nothing of the effects that a lifetime of dieting can have on your mental health or self-image.
People who do lose a lot of weight and keep it off have been the subject of research hoping to pinpoint something noteworthy that might inform better weight-loss studies. The National Weight Control Registry (NWCR) was founded by Rena Wing, Ph.D. and James O. Hill, Ph.D., in 1994 to gather information among those who have maintained at least a 30-pound weight loss for more than a year. Most individuals in the registry are women who have lost an average of 66 pounds and kept it off for five-and-a-half years by following a variety of low-calorie diets while engaging in high levels of physical activity (about one hour per day). According to the website, members also tend to weigh themselves at least once a week, eat breakfast daily, and watch less than 10 hours of TV per week. That being said, despite some core commonalities, there’s substantial variability amongst participants as to how they have maintained the weight loss. Most report substantial lifestyle changes, illustrating that there’s no single best approach or quick fix—six-week diets aren’t going to cut it.
While the registry provides helpful and encouraging evidence that for some, long-term weight loss maintenance is possible, we should be careful about how we interpret the data. For sure, some individuals can lose weight and keep it off, but that doesn’t mean that it is likely that most individuals will be able to. After all, we don’t have a registry of everyone who has tried to lose weight and been unsuccessful, but the research suggests this would far outnumber the success stories in the NWCR.
For a while after losing weight, I did attribute my weight loss to the diet. But the longer that I’ve maintained my weight and shifted my diet around over and over (and over), the more I realized that the actual food I eat isn’t the main thing that has enabled me to keep weight off. I’ve made a number of changes that have made it possible for me to commit to the dietary changes that facilitated the weight loss in the first place, including lots of physical activity, being mindful of my diet and hunger cues, and managing psychological stressors without relying on food. The longer that I have maintained the weight loss, the more I have come to realize much of what the research and clinician perspectives in this article highlight: Maintaining a weight-reduced state is a lifelong journey, many dietary approaches can work to facilitate weight loss and keep it off, and the overly prescriptive, over-hyped promises of our dieting culture are just a temporary bandage on a much greater issue. For many, many people, weight loss diets will fail. The important thing to remember is that it's not you, it's them.
Kevin Klatt is currently finishing his Ph.D. in Nutritional Sciences as well as the Registered Dietitian credential. Kevin's research uses cell, animal, and human feeding experiments to better understand human nutrient requirements. Additional information about Kevin's work, funding, and interests can be found here.
