April 06, 2007
All Diets Fail To Keep Off Weight

UCLA researchers confirm what you already know: diets do not work for sustained weight loss.

Will you lose weight and keep it off if you diet? No, probably not, UCLA researchers report in the April issue of American Psychologist, the journal of the American Psychological Association.

"You can initially lose 5 to 10 percent of your weight on any number of diets, but then the weight comes back," said Traci Mann, UCLA associate professor of psychology and lead author of the study. "We found that the majority of people regained all the weight, plus more. Sustained weight loss was found only in a small minority of participants, while complete weight regain was found in the majority. Diets do not lead to sustained weight loss or health benefits for the majority of people."

Mann and her co-authors conducted the most comprehensive and rigorous analysis of diet studies, analyzing 31 long-term studies.

The researchers analyzed all studies that followed dieters from 2 to 5 years. None of them worked. Worse, these studies contain biases that overstate the benefits of the diets.

Mann said that certain factors biased the diet studies to make them appear more effective than they really were. For one, many participants self-reported their weight by phone or mail rather than having their weight measured on a scale by an impartial source. Also, the studies have very low follow-up rates eight of the studies had follow-up rates lower than 50 percent, and those who responded may not have been representative of the entire group, since people who gain back large amounts of weight are generally unlikely to show up for follow-up tests, Mann said.

Dieting is even worse than not dieting.

"Several studies indicate that dieting is actually a consistent predictor of future weight gain," said Janet Tomiyama, a UCLA graduate student of psychology and co-author of the study. One study found that both men and women who participated in formal weight-loss programs gained significantly more weight over a two-year period than those who had not participated in a weight-loss program, she said. Another study, which examined a variety of lifestyle factors and their relationship to changes in weight in more than 19,000 healthy older men over a four-year period, found that "one of the best predictors of weight gain over the four years was having lost weight on a diet at some point during the years before the study started," Tomiyama said. In several studies, people in control groups who did not diet were not that much worse off and in many cases were better off than those who did diet, she said.

In a way this is great news for anyone who doesn't want to diet. You don't need to feel guilty about it. If you diet you'll just gain more weight in the long run. My guess is the body treats the scarcity of food while on a diet as a sign that it needs to build up fat stores in case another lean period happens.

So how to lose weight? The Mann and Tomiyama suspect that exercise will best keep people skinny. But their latest analysis was restricted to the effects of dieting.

People faced with morbid obesity can do the stomach surgey that restricts stomach size. That appears to work pretty reliably. Also, get enough sleep. Lack of sleep has been found a contributor to weight gain in other studies. Also, at least eat healthy foods regardless of how much food you eat.

I'd like to see more studies on the effect of eating various ratios of different types of fats and sugars. Does fructose consumption contribute to obesity? Do some fats sate hunger for longer than other fats? Do low glycemic index foods sate hunger for longer? In addition to how much we eat, what we eat might matter for weight control.

Share |      Randall Parker, 2007 April 06 11:04 AM  Aging Diet Studies

Robert said at April 6, 2007 12:24 PM:

Welcome to my world.

Larry said at April 6, 2007 7:20 PM:

Yes, exercise of the correct intensity and duration will, for 90% of the human population, prevent obesity. See the following article (excerpted):

"The Amish Paradox" (LA Times, Jan 12, 2004)
By Jeannine Stein, Times Staff Writer

"Despite a high-calorie diet, an Old Order [Amish] community's intensely physical lifestyle produces a strikingly low rate of obesity. It's a message for the modern world.

Forget the standard-issue health and fitness resolutions that include joining a gym, going to yoga and trading meatball subs for white-meat turkey. It may just be that the best way to get in shape is to plow the back 40, toss a few bales of hay and wash buckets of wet clothes by hand.

Call it the Amish paradox. An exercise science professor has discovered that a pocket of Old Order Amish folks in Ontario, Canada, has stunningly low obesity levels, despite a diet high in fat, calories and refined sugar exactly the stuff doctors tell us not to eat.

They're at a paltry 4% obesity rate, compared to a whopping 31% in the general U.S. population, which, as we all know, is getting fatter by the minute. This group of Amish manages to keep its overweight levels low despite a diet that includes meat, potatoes, gravy, cakes, pies and eggs. So what's their secret? Exercise, people. Exercise....

Amish men spent about 10 hours a week doing vigorous activities, women about 3 1/2 hours (heavy lifting, shoveling or digging, shoeing horses, tossing straw bales). Men averaged 43 hours of moderate activity a week, women about 39 hours (gardening, feeding farm animals, doing laundry)...."

I would also add a personal observation. Living in Ethiopia I observed a virtual absence of overweight or obese individuals, even amoung the wealthy section of the population. Typically these Ethiopians are moderately active for 30+ hours per week -- lots of walking. They can eat as much as they wish of the basic staples: injera (unleavened bread) and potato stew. With a fairly simple and boring diet, they only eat when their brain receives a signal that they're actually hungry. Contrast this with Americans -- we eat recreationally, for pleasure, just to "get our buds off".

Layperson said at April 6, 2007 7:36 PM:

Everybody who attentively follows this subject already knew that diets do not work and are in fact counterproductive. However, I do not think that the relationship between exercise and weight loss is simple or linear either. Sometimes and in some circumstances it seems to work, not so much at other times, and the underlying factors are murky.

May I recommend "The Slow Down Diet" by Marc David, which confirms this latest study as well as my own observations. It is not at all about dieting, despite the title. It stresses that HOW and WHEN and in what state of mind we eat, matters just as much as quantity. Probably something similar is true of exercising.

Randall Parker said at April 6, 2007 8:25 PM:


The problem is that most of us do not have 50+ hours to spare for moderate to intense physical activity.

What I want to know: How many hours of exercise is needed to keep off the weight?

Also, is the weight reduction due to:

1) More calories burnt while doing the work.

2) More muscle mass built up so that more calories get burnt even while sitting around.

3) A hormonal effect that exercise has on the body.

john said at April 6, 2007 9:03 PM:

Why would HIGH glycemic foods keep you sated for longer. That's the opposite of what nutritionists tend to believe. Care to explain?

Joshthenutritionist said at April 6, 2007 9:55 PM:

After reading the comments posted thus far, I have a few thoughts of my own, in regards to exercise, based on the current research to maintain cardiovascular health and muscle strength, you need to do a minimum of 30 minutes of moderate intensity exercise five or more days of the week. This does not need to be anything more then brisk walking as an example. For the vast majority of people residing in the US today, it is not practical to try and maintain a healthy body weight through exercise alone with little to no thought on food intake. Most of use by where we live and work are basicly forced to spend most of our time sitting, which does not expend much energy. This being the case, the main focus should be on what one chooses to eat. This goal can be achieved by choosing to eat foods that contain the most essintial nutrients while having a low caloric density. What magical foods do I speak of, I hope you are sitting down, drum roll..., fruits and vegetables!! Year after year studies come out that Americans are well below optimal intake of fruits and espically vegetables. These foods will give you the micronutrients and macronutrients your body needs for optimal health while providing you with plenty of fiber to fill you up. Now you might be thinking what about whole grains, low-fat dairy and lean proteins, well, your right you do need moderate amounts of these foods as well, but focus on getting all the fruits and vegetables you can handle before you even think about eating anything else and I'm telling you from professional and personal experience your well on your way to a healthy body weight. Oh and in terms of your body's glycemic response to food, look into glycemic load, you want to try and eat the foods that have the lowest GL, this way your body has a low consistent blood sugar and steady insulin release, so you don't wear your hard working cells out.

dave tweed said at April 7, 2007 6:14 AM:

"People faced with morbid obesity can do the stomach surgey that restricts stomach size." There's unresolved debate about whether it's stomach size that's important (no links, sorry). Apparently the initial stomach surgery procedures involved essentially "isolating" surgically large volumes of the stomach which _may_ have drastically reduced the hormone ghrelin's secretion. Newer less invasive methods like gastric bands apparently restrict volume without actually removing the tissue and _apparently_ this doesn't reduce ghrelin secretion. There may be some evidence that these don't work as well at reducing appetite, and hence eating behaviour, as the older but more invasive methods.

Anyway, practical upshot is _maybe_ we can learn how to (without long-term pharmacological intervention) manipulate hormone levels to get the same effect as stomach surgery, i.e., maybe a short course of some drug could somehow switch off some proportion of the ghrelin producing cells. (I'm not knocking the comments about nutrition & exercise above, but I spend about an hour a day walking everywhere and I don't have time for even more execise, so something to blunt my appetite would be useful.)

Randall Parker said at April 7, 2007 7:40 AM:


The "high glycemic index" should have been "low glycemic index". I fixed it. Sorry about that.

Randall Parker said at April 7, 2007 7:45 AM:


We could redesign our work environments to let us more easily get exercise. For example, suppose you are in a work training class (e.g. on workplace safety, intellectual property protection, security, or waste handling - to name some I've had to attend in the last 6 months). If a room was equipped with exercise cylces and a projector people could watch the training while getting moderate to intense exercise.

We could do the same with a lot of status meetings. Exercise while waiting to take your turn describing where you are at in your work.

Julian Morrison said at April 7, 2007 12:52 PM:

After seeing the pictures on this site I went looking for info on the technique he used, HIIT, and the evidence does seem to be quite good for it.

Who's up for a burger? said at April 7, 2007 1:00 PM:

I don't read the research as saying that diets cause weight gain, but rather that those who try diets are losing their battle anyway and that diets are one more thing they can't stick to. I'd say causality's arrow points from weight gain to (usually unsuccessful) dieting.

OTOH, there are people who at some point in their lives turn the corner on their weight. I'd like to see research about what characterizes them.

I exercise a good bit more than average, but exercise has not put my appetite and my calorie needs in balance. My trick is the mental judo that lets me equate hunger pangs with "I'm not gaining weight right now. Good!" rather than "who's up for a burger?" It took many years to work that one out.

Joey said at April 7, 2007 1:40 PM:

My daughter is 16, weighs 164, is 5'4" tall. She believes she is fat and she's larger than most of her friends. She wants to lose weight. Already she's an avid tennis player, tries to watch what she eats (though is a bit heavy on the carbs), and is starting to add regular work-outs at the gym to her regimen. Genetically she has a tough row to hoe. I'm a powerlifter and am very thick though not necessarily fat -- and I spent a lot of time doing cardio exercises.

If "dieting" is not a good idea (and I wasn't real happy about a 16-year-old dieting anyway), what should she do differently? (She has a great personality, but as she moves further into highschool she is, as one would expect, becoming more and more anxious about her weight.)

Thanks in advance for any advice.

Joshthenutritionist said at April 7, 2007 3:48 PM:

I'm enjoying this dicussion, Randall, in a perfect world I love to see such things in office workplaces, I can only speak of my own experience and from people I know and none of them could see exercise equipment being implimented into their workplaces, but I like how your thinking outside the box, again if you look at the epi data the vast majority of people in the US are consuming little to no fruits, vegetables and fiber. If you consume the needed amounts of fruits, vegetable, fiber and water, which for the average adult male is 4.5 cups of wholes vegetables, 2.5 cups of whole fruit, 40 grams of fiber and 80 oz of water, and you can still tell me you are hungry all the time, I will personally pay for your stomach ring. Otherwise do what one poster noted and live a Amish lifestyle, do that, and you can eat all the calories you want, but you won't have much time for futurepundit.com now would you:)

Randall Parker said at April 7, 2007 4:27 PM:


The perfect world: Well, lots of things become possible. Google lets people bring their dogs to work. Who'd've expected that? So does a company in my town. I wouldn't rule out exercise equipment in workplaces as impossible. It just takes some enterpreneurs to say "Hey, I want to exercise when I am listening to hours of status from engineers and marketers and bean counters" and suddenly one company does it. If the company prospers others will follow. Best if the company is a high profile success story like Google.

I'm a great believer in putting out-of-the-box ideas up on the web. It is one of the reasons I write this site. Someone has to be the first person to make an argument in a public forum before the idea has 2 and 3 and 4 people advocating it. So I say again: Put aerobic exercise machines in meeting and training rooms so that people and work out and do meetings at the same time.

As for eating fruits and vegetables: I eat enough fruit. But I'm still lagging on the vegetables. I'm pessimistic on veggies as a solution only because we've been hearing a steady message for years on the benefits of veggies and yet average vegetable consumption has gone up hardly at all.

Maybe if a veggie diet study gets done and a book is written and an Oprah appearance made extolling the vegetable diet as the route to weight loss some might try it. After all, the desire to lose weight and look good now is far stronger a motivator than the desire to avoid heart disease 20 or 30 years from now. But we need that popularizer. You want to sign yourself up to do that? Think you'd present well on Oprah?

Joshthenutritionist said at April 8, 2007 12:22 PM:

Randall, haha, not sure if I am ready for Oprah, what in the world would I wear:), I couldn't agree with you more for the need to implement new workplace environments in an attempt to address our growing obesity problem. I'm glad to hear that you are successful in eating enough fruit daily, your cells thank you for that, I can't agree with you though that based on the lack of increases in consumption of vegetables by Americans you feel that optimal vegetable intake is without merit.

Just take a look here, http://www.hsph.harvard.edu/nutritionsource/fruits.html The authors of this article brake down the benefits of fruits and vegetables, for example for cardiovasular disease they state, "The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30% less likely to have had a heart attack or stroke.
Although all fruits and vegetables likely contribute to this benefit, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions."

The masses are slow react, just because people still choose to smoke, drink, eat food that is high in calories, saturated and trans fats, high in sodium, simple sugars, and often times lacks fiber, micronutrients and phytochemicals doesn't mean that we don't have strong scientific evidence which shows the harm or benifits of these things. There are major underlying nuerological pathways that drive us toward destructve behaviors, couple that with the advertising nightmare we live in, which tries, very succesfully, from basicly birth to tell us what we should eat, drink, etc. This makes it extremely difficult for people to choose to consume the right foods in the proper amounts on a daily basis, that I'll give you but don't tell me a man of science such as yourself doesn't think the evidence is there.

Randall Parker said at April 8, 2007 1:14 PM:


I agree that the evidence is there wrt vegetable consumption and health benefits. But my point is that the public doesn't like vegetables. Telling them to eat more vegetables doesn't seem like it has worked or that it will work.

Maybe vegetables can be made more palatable somehow?

Myles said at June 14, 2007 1:58 PM:

I think these findings are interesting, and confirm what I would already have assumed, but the scope of the research falls short of providing any clear answers to the current epidemic of obesity. OF COURSE dieters tend to gain more weight in the long run - aside from any metabolical imbalances caused by dieting, dieters tend to have poor diet and exercise habits TO BEGIN WITH that have already set them well down the path to a life of obesity. If they had developed good diet and exercise habits earlier in life, they wouldn't have any need to go on a "diet." For example: I have often noted that people who drink large quantities of DIET soda, purchase exercise videos, and have little weights at home (often in front of the TV) tend to be some of the MOST out-of-shape people. These individuals may realize (and then lose) some small short-term gains, but the very fact that they are still constantly trying to drink soda (be it diet or not) and be in front of their television implies that their habits have not fundamentally changed.

I would be curious how the study defined a "diet." What about diets versus LONG-TERM changes in peoples' diet and exercise habits? This is the inherent flaw with a "diet" - it is by definition TEMPORARY. I'm not overweight, and I've never been on a diet, but if an obese person were to examine my everyday diet and exercise habits, it would probably follow pretty closely how they would define a "diet" (e.g., exercise regularly and don't eat junk food regularly - what a concept!).

I absolutely agree with the conclusion of the study: that overweight individuals should not go on diets - in the long run, all they're doing are enriching the industry of snake-oil salesmen who peddle get-skinny-quick solutions. However, I disagree with the implication that no one should make drastic changes to their diet and exercise habits. The real answer to weight loss is far less glamorous than The South Beach Diet would have overweight people believe: instead of short-term solutions - the gains of which will ultimately disappear - people need to make simple but sweeping changes for the REST OF THEIR LIVES. The food you eat becomes a bit less tasty and you can't eat as much of it, dessert and candy (and I include soda in this category) become true "treats" and not part of everyday consumption, and you need to move your butt off the couch and out of your cubicle an hour or two every day. Not very sexy, but a proven method to remain close to a healthy weight for the rest of your life.

Nor does the study address the simple "calories in = calories out + fat" equation. How can exercise be the ONLY option? A change to healthier eating habits will surely lead to a reduction in calories which will, for the vast majority of people, lead to weight loss (or at least no additional weight gain). I think the crux of the matter has more to do with peoples' will-power to self-motivate and self-regulate themselves such that they can maintain healthy habits. In short: diets are an "easy way out." However there is no easy way out. Therefore of course diets will always fail, they're an inherently invalid solution. Kudos to the researchers for proving what I already could have deduced, but I disagree with many of their subsequent conclusions.

Mike said at May 20, 2009 10:31 AM:

The interesting question remains: what causes people to eat large quantities of animal proteins?

anonymous said at January 30, 2010 10:26 AM:

From my personal experience, animal products are somehow connected to addiction. I smoked cigarettes for three years, from age 15 to age 18. I tried quitting several times. I think it was the third time trying that I decided to go vegetarian and eat more vegan food. This time I was able to quit smoking and I am 21 years old now and dislike cigarettes and secondhand smoke. I went back to eating meat and now I feel more sluggish and stressed. I am working toward a vegan diet again now and exercising every day.

Does anyone know of any scientific studies connecting animal products to cigarette, cocaine, or even heroine addiction?

anonymous said at January 30, 2010 11:12 AM:

I think another interesting question that remains: how many calories do students burn studying at school and at home? How many calories do scientists burn when they perform difficult research?

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