The diet industry makes about 72 billion dollars a year in the United States alone. That number would be a lot smaller if diets actually worked long-term. The uncomfortable truth, backed by decades of research, is that most diets fail. Not because people lack willpower, but because the diets themselves are designed in ways that make failure almost inevitable.
A 2020 meta-analysis published in The BMJ reviewed 121 clinical trials covering nearly 22,000 participants across 14 popular diets. The average weight loss after six months was 4-5 kg. By 12 months, most participants had regained a significant portion of that weight, and the differences between diets were statistically insignificant. Keto, paleo, low-fat, Mediterranean, it did not matter much. The pattern was the same: lose weight, then regain it.
So what is going wrong? And more importantly, what works instead?
The restriction-binge cycle
Most diets work by eliminating something. Cut carbs. Cut fat. Cut entire food groups. The initial weight loss comes from creating a calorie deficit, which any restriction will do. But the elimination itself creates a psychological pressure that builds over time.
Research on dietary restraint, going back to the 1970s work of psychologists C. Peter Herman and Janet Polivy at the University of Toronto, shows that the more rigidly people restrict their eating, the more likely they are to overeat when they eventually break the rules. They called this the "what the hell" effect: once a dieter eats a forbidden food, they tend to abandon all restraint for the rest of the day or week.
I have seen this play out with hundreds of people. They are perfect on their diet from Monday to Thursday. Friday night they have a slice of pizza, which was not on the plan, and then they spend the entire weekend eating as if the diet never existed. Monday they restart with a mix of guilt and determination, and the cycle repeats. The net result over months is often zero progress or even weight gain.
Your biology is working against extreme diets
Beyond the psychological problems, your body actively resists aggressive dieting. When you cut calories significantly, several hormonal changes kick in. Leptin, the hormone that signals fullness, drops. Ghrelin, the hunger hormone, increases. Your metabolic rate decreases beyond what weight loss alone would predict.
A 2011 study in the New England Journal of Medicine measured these hormonal changes in dieters after a 10-week very-low-calorie diet. Even 12 months later, their hunger hormones had not returned to baseline. Their bodies were still hormonally pushing them to regain the weight. This is not a willpower problem. This is endocrinology.
The good news is that more moderate approaches, where you create a smaller deficit and lose weight slowly, produce less dramatic hormonal pushback. Losing 0.5-1 pound per week is not as exciting as losing 5 pounds in a week, but it is far more likely to stay off.
What works instead: the identity shift
The people I have seen succeed at long-term weight management share a common trait: they stopped dieting and started changing their identity. There is a difference between "I am on a diet" and "I am someone who eats mostly whole foods." The first is temporary. The second is who you are.
James Clear writes about this in Atomic Habits: every action is a vote for the type of person you want to become. When you choose grilled chicken over fried chicken, you are not suffering through a diet rule. You are voting for being someone who makes good food choices. That reframe matters more than it sounds.
The practical version of this is to focus on building habits rather than following rules. Habits are automatic. Rules require willpower. And willpower is a finite resource that runs out, usually around 9 PM when you are tired and the ice cream is calling.
Five habits that replace dieting
Instead of following a diet with a start date and an end date, build these into your daily life permanently. You do not need to implement all of them at once. Start with one, make it automatic, then add the next.
- Eat protein at every meal. Aim for 25-40g per meal depending on your size. This single habit improves satiety, preserves muscle, and tends to naturally reduce overall calorie intake. A 2005 study at Purdue University found that higher protein intake reduced snacking by 50% in the evening hours.
- Cook more meals at home. People who cook at home five or more times per week consume about 140 fewer calories per day than those who cook less, according to a 2014 Johns Hopkins study. You control the ingredients, the portions, and the cooking method.
- Walk daily. Not as exercise but as a baseline activity level. The calorie burn from walking adds up more than most people realize, and unlike intense workouts, it does not increase appetite. Aim for 7,000-10,000 steps.
- Stop eating when you are 80% full. The Japanese concept of hara hachi bu. It takes about 20 minutes for fullness signals to reach your brain, so stopping before you feel completely stuffed usually means you ate exactly the right amount.
- Sleep seven to nine hours. Sleep deprivation increases calorie intake by an average of 385 calories per day according to a 2016 meta-analysis in the European Journal of Clinical Nutrition. Good sleep is a weight loss strategy that requires zero dietary changes.
The accountability piece that most people skip
Here is something the research consistently shows: people who have some form of external accountability lose more weight and keep it off longer. A 2019 study in Obesity Science and Practice found that participants who had weekly check-ins with a coach lost twice as much weight as those who tried to lose weight on their own.
The mechanism is simple. When you know someone will ask about your week, you make slightly better choices. Not perfect choices. Just slightly better ones, consistently. And that consistency compounds.
This is where tools like BodyBuddy come in. Daily check-ins via text create a lightweight accountability loop that does not require scheduling appointments or driving to a clinic. You text about your meals, your struggles, and your wins, and you get coaching back. It is not about perfection. It is about staying connected to your goals even on bad days. Try it at bodybuddy.app.
Frequently asked questions
If diets do not work, how do people lose weight?
People lose weight by eating fewer calories than they burn, but the method matters. Sustainable habit changes that create a moderate calorie deficit work better than aggressive short-term diets. The National Weight Control Registry, which tracks people who have lost 30+ pounds and kept it off for a year or more, finds that successful maintainers overwhelmingly use moderate, consistent approaches rather than extreme diets.
Is there any diet that actually works long-term?
The research suggests the best diet is whichever one you can stick to. That usually means it is not too restrictive, includes foods you enjoy, is high in protein and fiber, and does not require you to eliminate entire food groups. Mediterranean-style eating patterns have some of the best long-term adherence data.
What about intermittent fasting?
Intermittent fasting can work, but the research shows it works primarily because it reduces total calorie intake, not because of any special metabolic effect. A 2022 NEJM review found that time-restricted eating produced similar weight loss to standard calorie restriction. If a shorter eating window helps you eat less naturally, use it. If it makes you overeat during your window, it is not the right tool for you.
The bottom line
Diets fail because they are temporary solutions to a permanent challenge. The alternative is to stop dieting entirely and instead build sustainable habits: eat enough protein, cook at home more, walk daily, respect your hunger signals, and sleep well. Add some form of accountability, whether that is a coach, a friend, or an app that checks in with you. These are boring answers compared to "lose 20 pounds in 30 days," but boring answers are the ones that work 18 months from now.