What is the most effective diet for losing weight?

Cut the calories–and the crap


Kyle May/Flickr

This past weekend, Science-ish was disappointed to read Margaret Wente’s column on health evidence, in which she opined: “Today’s health wisdom has a way of becoming tomorrow’s bunk… This may help explain why all the standard diet and exercise advice is worthless.” Sure, evidence about the best way to eat is evolving, the media screws up reporting on science all the time, and the health sciences are particularly vulnerable to what Edmonton-based health law professor Timothy Caulfield calls, in his insightful new book A Cure for Everything!, “an unprecedented number of perverting influences” like Big Food.

But that’s no reason to discount science altogether. When you look at the evidence about diet, some things are pretty straightforward. So rather than taking a blind approach to a healthy life, Science-ish will stick to the science, and give you the six things you should know about an evidence-based approach to diet and weight loss.

1. Surprise, surprise! There is no “best” diet for losing weight.

Science-ish found research to prove that just about every diet imaginable works when it comes to losing weight. As the authors of this study point out, “Several trials showed that low-carbohydrate, high-protein diets resulted in more weight loss over the course of three to six months than conventional high-carbohydrate, low-fat diets, but other studies did not show this effect… other researchers found that a very-high-carbohydrate, very-low-fat vegetarian diet was superior to a conventional high-carbohydrate, low-fat diet.”

And on and on and on.

Now, this isn’t because the science is necessarily bad or purposefully misleading. It doesn’t mean we should throw our hands in the air and live on chocolate and burgers. The variability in results is caused by a few things: Good studies about the effects of diet need to be long-term and long-term studies are expensive; tracking people over time and getting them to adhere to their assigned diet is difficult; bias sometimes influences the results of the study; and science is an iterative process so things change as research evolves, which—when reported without context—can be confusing.

But, when taken as a whole, the evidence suggests it doesn’t really matter what diet you follow—low carb, high protein, Atkins, whatever. When it comes to losing weight, it’s cutting calories that counts.

Here’s some evidence: this trial looked at long-term results of diets with different ratios of carbohydrates, fat, and protein and found that “the diets were equally successful in promoting clinically meaningful weight loss and the maintenance of weight loss over the course of 2 years. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets.”

Another randomized trial looked at some 300 premenopausal overweight and obese women for 12 months as they each followed one of four weight-loss diets: Atkins (very low in carbohydrates), Zone (low carb), Ornish (very high carb), and LEARN (low in fat, high in carb, based on U.S. national guidelines). Conclusions? Those assigned to the Atkins diet lost more weight and had more favourable outcomes for metabolic effects after one year than the women who went on the other diets. But the implication of this study, researchers suggested, is that weight loss with a low-cab diet is “likely to be at least as large as for any other dietary pattern.”

The journal Public Health Nutrition published a trial comparing the effects of Atkins, the Slim-Fast Plan, Weight Watchers Pure Points program, and the ‘Eat yourself Slim’ Diet and Fitness Plan against a control diet for six months. Participants here were overweight and obese men and women, aged 21 to 60. No difference was observed among the groups at six months, and all groups lost between five and nine kilograms.

The take-home message is pretty simple: when people eat less, and stick to eating less, they will lose weight—no matter the diet. If you want to slim down, figure out a way to eat less that works for you.

2. The basics of a healthy diet are known.

The seemingly ever-changing advice about how to eat is confusing. More avocados, no avocados, some wine, no wine. But it’s confusing because reporters publicize single studies about the details of diet, which change as science incrementally moves along. While the details of a healthy diet are working themselves out, Caulfield told Science-ish, “There has been very little flip flopping on the basics of a healthy diet. We know what it looks like: fruits, veggies, whole grains, lean meats, et cetera.”

He’s not the first to point this out. In recent years, the foodie activist-journalist Michael Pollan as well as as the British debunking doctor Ben Goldacre—among others—have done good work in this area. In particular, I like this Goldacre tirade against the complicating forces of nutritionists: “Diet has been studied very extensively, and there are some things that we know with a fair degree of certainty: there is convincing evidence that diets rich in fresh fruit and vegetables, with natural sources of dietary fibre, avoiding obesity, moderate alcohol, and physical exercise, are protective against things such as cancer and heart disease. But nutritionists don’t stop there, because they can’t: they have to manufacture complication, to justify the existence of their profession.”

3. Cut the crap.

When you’re cutting calories, you need to leave enough room in your diet for those things that your body needs to stay healthy—fruits, vegetables, lean protein—and this means you need to cut the crap. A good place to start is by eliminating all pop, juice, and junk food, Caulfield suggested, adding that half of what’s on your plate should be fruits and vegetables. (Think of Pollan’s famous adage: “Eat food. Not too much. Mostly plants.”)

As Science-ish has noted before, consuming sugary drinks, processed meats, and potato chips has been correlated with weight gain in a previous cohort study while eating vegetables, fruits, nuts and yogurt has been correlated with less weight gain. (Remember, correlation is not causation, but it’s something to think about.) As well, this 2010 Harvard study on sugary beverages and the risk of obesity and type-2 diabetes found that epidemiological reports “clearly indicate that regular consumption of (sugar-sweetened beverages) can lead to weight gain and substantially increase risk of developing chronic diseases including (metabolic syndrome, diabetes, and coronary heart disease).”

Caulfield, an evidence nerd who put himself on a diet to test his theories and lost 25 pounds, put it simply for Science-ish: “We need to eat fewer calories—forever. Not just during the dieting period, but long term. So we need to figure out what we can cut and what you can’t give up. Eat the latter in moderation.”

4. Sticking to a diet is tricky; make a lifestyle change.

Having thrown that “keep it simple” advice out there, Science-ish must acknowledge that doing so is incredibly difficult for us mortals. This trial found it was so difficult to get people to adhere to their prescribed diets, that studying different diets was damned near impossible. “Despite the intensive behavioral counseling in our study, participants had difficulty achieving the goals for macronutrient intake of their assigned group,” the study read.

In a fascinating editorial related to this study, the author notes: “The inability of the volunteers to maintain their diets must give us pause. . . even these highly motivated, intelligent participants who were coached by expert professionals could not achieve the weight losses needed to reverse the obesity epidemic.” The writer goes on to suggest the remedy may be community overhaul, pointing to studies of two small towns in France, in which everyone from the mayor to restaurant owners joined together in an effort to get kids to eat better and exercise more. Over five years, “the prevalence of overweight in children had fallen to 8.8%, whereas it had risen to 17.8% in the neighboring comparison towns, in line with the national trend.”

For now, one message we can take from this is that lifestyle changes are needed to sustain weight loss. As Caulfield told Science-ish, “It is a cliché, but I’ll say it again: it must be a lifestyle change, not a ‘diet.’ ” Science-ish would offer Rob Ford, Toronto’s mayor, that wisdom, as he publicly attempts to lose weight before the summer in a very smart PR trick. Think about the rest of your life, Mayor Ford, not just the summer—or the next election.

5. Tracking helps.

Counting calories may seem retro, and not in a fun way. But those who track what’s going in and frequently weigh themselves have better weight-loss outcomes, which is particularly helpful since studies have found people underestimate calories in the food they eat, especially high-calorie foods.

6. Be aware of the mind-bending forces of industry and culture.

As you have surely noticed by now, there are some evidence-based things we know about what works to help people lose weight. But somehow, the wisdom about what makes us healthy has been twisted to the point that we don’t recognize these simple truths—a statement Caulfield makes very convincingly in his book.

In fact, I wonder whether we’d have a better chance at keeping extra weight off if we had less messaging about junk food around us. Some cities are already taking steps in this direction. But until Mayor Ford’s weight loss regime is extended into a province- and nation-wide health overhaul, Science-ish will leave you with some of Caulfield’s sound advice:

“Be conscious of all the twisting forces that exist in our culture (and within us) that are constantly trying to pull us from a pattern of healthy eating. These forces include our own misconceptions about ourselves and what we eat… Refuse fast food. Don’t get tricked into accepting big portion sizes. Don’t let social pressures—friends, work situations, travel—derail healthy eating. And don’t get bamboozled by the ‘healthy’ or ‘organic’ labels on packaged food. These are, by and large, marketing tools… Simplicity is the revelation.”

After my year-end call for submissions, you told me you were most concerned about two things: whether WiFi poses health risks, and which is the most effective diet for losing weight, based on the evidence. This is the last installment in that series.

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at julia.belluz@medicalpost.rogers.com or on Twitter @juliaoftoronto


What is the most effective diet for losing weight?

  1. Thank you for this.

    All my life I’ve seen people go on and off diets…..and they swear by each and every one of them, but none of the diets seem to work more than temporarily.

    Yet after say…20…different diets that don’t work…..they are just as eager to try the 21st until the find THE diet that does work.  And there never is one….just a lot of hype.

    No fat, no wait…no sugar…no wait…no carbs….blah blah blah

    Less food, more exercise… instead….thank you!

  2. I went to Korea 15 years ago and it completely changed how I thought about food and Western diet. 

    At first, I thought I was going to starve to death because I couldn’t use chopsticks and I didn’t want to use fork forever. I also got hungry an hour or two after eating a big meal. After a couple months I was using chopsticks and eating lots of vegetables, rice and a little meat/fish in each meal – didn’t differentiate between breakfast, lunch, dinner.  Even our utensils facilitate more eating – eat slower with chopsticks than you do with fork. I had to teach myself how to cook when I returned from Korea because I no longer enjoyed how Western society eats food.

    One of english classes I taught was a group of medical students who were fluent in english and all I had to do was lead discussions about whatever I felt like, students just want an hour or two a week to talk in english. One day, the students wanted to talk about why Korean medical community thought most North Americans were fat compared to Koreans/Asians: 

    1) Sugar – don’t do desserts over there, no choc bars, sweets, chips, cakes …. etc. Fewer pure sugar products in Korea. Also use honey and other natural sweeteners like grated apples/pears in recipes and reduce amount of sugar use.

    2) Grains – Koreans eat rice but few other grains. Wheat is controversial product, as Maclean’s well knows.

    3) Too much meat, not enough vegetables/rice. Koreans mocked our diet – large slabs of meat, with a tiny potato and a few leafs of lettuce – North Americans still eat like cavemen according to Korean doctors. And lean meat can kiss my grits – I just got some pork belly from asian market. We need fat but everything in moderation tho.

    North American consumption of calories has sky rocketed over past 30 years or thereabouts, we eat more processed food and sugar but we also eat more fresh fruits and veg because we have year round supply of most products now.

    I would like to do some social engineering and have our schools teach pupils how to cook food – fresh food is superior and people just have to know how to prepare it.

  3. I think the idea of “going on a diet” (instead of making permanent lifestyle changes) is a real problem, and one of the reasons many people don’t succeed. Our bodies have a hormone called leptin, which regulates metabolism. As people lose weight, leptin levels decrease, slowing metabolisms and causing food cravings to spike. After they “go off the diet” they quickly regain lost weight, given their slow metabolism. Now they’re fat again, and often have less muscle mass than in the first place. 

  4. Sugar makes you fat. High fructose corn syrup really messes with the body’s ability to regulate fat. 

    Fat itself does not make you fat. Yes, have another rib eye and for God sake, do enjoy your bacon and eggs. Please, though, skip the pop, dessert, and the Wonder bread. i.e. the crap. 

    • Sugar is what your brain operates on.

      All of this stuff is necessary….salt, fat, sugar, carbs, protein etc…and some things that are just a nice treat.

      Like the Greeks said…..Everything in moderation

      • While it is true that the body ‘operates” on glucose (sugar), in actuality, carbohydrates and other foods are broken down into glucose by the digestive system (enzymes) so a person does not need to eat sugar.  Sugar has no food value, neither does white flour.  The body does need fats, protein, complex carbohydrates that you get through fruits and vegetables.   I consider a piece of watermelon, pineapple or cantelope a treat.  I just try not to eat anything that doesn’t have any nutritional value.

        • “I consider a piece of watermelon, pineapple or cantelope a treat.”

          1 watermelon wedge provides a third of your daily vitamin A needs, 39% of your vitamin C needs, 5% of your fibre and 2 grams of protein. The calorie count is 86 ( http://nutritiondata.self.com/facts/fruits-and-fruit-juices/2072/2 ). 

          I’d say watermelons are a pretty defensible party of a healthy diet. 

          • Yes, that is what I mean….you can totally eliminate processed ‘junk” food from your diet and get all your sweets (fructose) from natural sources (fruits) that have tons of nutritional value and fibre as well.  I wasn’t saying I ‘only eat watermelon, etc as a treat”…I was responding to Emilys assertion that people need processed sugar and a “the occasional treat”.  I am just stating that fruits contain plenty of natural sugar.  Not that I think it is an issue to eat processed sugar on occasion…I just don’t think anyone needs it to survivie.

          • Emily said your brain operates on sugar…you added the processed, and needing a treat to survive, part.

          • Fair enough – I was imagining a poor, guilt-wracked Healthcare insider sneaking into the fridge at night for an  extra watermelon wedge.

            That said, I don’t think treats are a bad thing. I try to satisfy my nutritional needs efficiently, freeing up calories for important things like beer. 

          • Hahaha….love the “sneaking into the fridge…”  No!  I eat all the fruit and vegetables I want.   I used to be a sugar fanatic but find those things “too sweet” now that I have been off them for 3 years.  The first two weeks were difficult but after that the cravings were gone.  Instead of potato chips, I eat a small handful of almonds…filling and healthy and crunchy and of course tasty.

      • I don’t eat sugar. Yes, some of the food I eat is converted to gulcose, like protien via glycogenesis, but the vast majority of the fuel my body has run on for the past four years has been ketones.

        As for moderation, I used to eat that way and it gave be an a1c of 6.8%. Today, and since 2009, my a1c has bounced between 4.8 and 5.0%.

      • Well, yeah sort of. Glucose is what your brain operates on, and glucose is manufactured by the body using the ingredients at hand (and yes, that includes protein).

        As for everything in moderation, we need to ditch that. Even if you eat crap processed food in moderation, you will get fat. The old calories in/calories out model has been absolutely debunked in the last 5 years or so (see Taubes et al…)

    • And FCS is in everything – things that aren’t even sweet.  It’s distorted people’s taste buds, just like the excess salt in processed foods.  I’m convinced we need to raise children to like real food, not by preaching that  it’s good for them, but by demonstrating to them it tastes better.

      • I saw a very interesting interview about a fellow who doesn’t eat anything his grandmother would not recognize as food…so he doesn’t eat margarine…only butter.  He doesn’t eat anything with bizarre additives.  Probably a really good idea.

        • Must never have seen a root cellar in spring.  LOL

          • I think he just means that he prefers to eat fresh fruits, vegetables, baked goods from the local bakery, meat from the local butcher shop, real dairy products.  He doesn’t eat packaged cookies with palm oil that six months on the shelf or mashed potatoes in a box or chili in a can. 

  5. I think Millo from “Bloom County” put it best when asked what diet Opus should use: “eat less and exercise more”.

    • Props for the Bloom County reference.

      Ack!  Thbbft!

  6. Here I am again on Maclean’s science blog questioning the power of science. In other words, I find it odd that losing weight is being reduced to a matter of science. Many people who lose weight do so without recourse to a science textbook, and there are factors beyond science, such as emotions, lifestyle, experience, etc, that contribute to gaining weight and, as a result, to losing weight, too.

    I suppose studies can tell us what foods can lead to a healthier lifestyle and body, but I don’t think science can tell us how to get there, or that those foods are the only way to get there. Things like cutting back, eating less frequently, and developing better habits can get you there, too, and I think it’s kind of arrogant to suggest that it’s science that tells us all this. Common sense, experience, and even the human touch have a lot to do with it, too.

    • I agree with you absolutely that psychology plays a huge part in issues of weight loss and weight loss retention but science does teach us the body’s nutritional requirements and things about satiation.  For instance through science we know that certain vitamines and minerals are essential to the body and that if we rely to heavily on certain sources of nutrition (ie: very lean meat and no vegetables or fats) it can actually be detrimental to our health (rabbit starvation, a time of protein poisoning or malnutrition) can occur.  I will never forget reading about a group of university students who got scurvy while living in together because their diet was mostly mac ‘n cheese.
      Science also teaches us if we don’t eat fat, protein and complex carbs we won’t feel satiated for any period of time. Our blood sugar with shoot and then drop like a stone when the insulin kicks in.  Suddenly we are hungry again because we have feasted on simple carbohydrates. 
      If we maintain a steady blood sugar with small frequent meals of complex carbs, fats & protein, we will keep us satiatied and our metabilism in high gear because our body won’t go into starvation mode.  Also, we know that we need to exercise because that keeps our bodies fit and ourselves happier.

      • Well, I guess it’s not surprising that you’re still on here overstating the power of science.

        No, science doesn’t have everything to say about why we get full. Emotions and experience are parts of the equation, among other things. If it was as simple as a scientific equation, all we’d have to do is plug people, and get the result. But that doesn’t happen, does it.

        And, no, we don’t need science to tell us that a balanced diet is necessary for proper nutrition.

        Your blood sugar theory is only part of it. Simply switching from bigger and less frequent meals to smaller more frequent meals makes a difference of about 10 or 20 pounds. It’s not the solution for truly obese people.

        And, again, it’s not that science isn’t part of diet knowledge, it’s that people reduce all diet knowledge, expertise and advice to science.

        This phenomenon of science worship runs deeper than I thought.

        • Whatever you want to call the study of human anatomy and physiology is your business…don’t call it a “science” if that affects your tender sensibilities.  How exactly do you think we know about how the digestive system works and information about the effects of diet on the body….
          I guess there is no reason why EVERY physician who counsels overweight people that their first degree is in science….in fact the PhD students that assisted us in the anatomy and physiology cadaver labs were science PhD candidates.  After obtaining their PhD, they were going to apply to the school of medicine.  Funny how that works,  everyone at the medical school had a science background.  They are all worship science.  No one had graduate under-graduate degrees in theology or arts.
          My comment about eating frequent small meals was to keep blood sugar regulated…to keep yourself from feeling hungry…to give you better odds at accomplishing your diet goals….it works for everyone on a diet.  The more you have to lose, the longer you need to stick at it to reach you goal.  The process is still the same. 

        • I don’t think the word “science” means what you think it means. 

          • Really. And what do you base that on?

  7. I heard someone once say that they were losing weight on the miracle “eat less, exercise more, and lose a small amount of weight consistently over a long period of time” diet. Not a catchy name, but complete and accurate.

  8. One of the things I always find infuriating is that there’s a a counterstudy for every study, no matter the subject. This includes fitness and health info. And every study, no matter what, is delivered while invoking a certain amount of authority. This fuels the fadishness of health and diet information while heaping suspicion on the purveyors of such info. I remember reading a well-known health magazine that argued against stretching and thinking: “really? This is crap. Because I now do regular stretches (especially my ITB) I’ve pretty much eliminated the knee pain that’s bothered me for years.” To the point: I think what Wente was say is, there’s a lot of crap info out there and maybe it’s best to do what makes you happy within reason and while using common sense. I can subscribe to that. I’m not sure why you would use her article as a jumping off point. Maybe you’re just lazy. Sorry.

  9. Low carb, high fat worked for me. It has now for over four years. Of course I’ve met successful losers that follow plans like Weight Watchers, but I was never successful with that. Alas, be it LCHF, WW, Ornish or whatever, if you don’t make it a lifestyle change for keeps, you won’t be one of the 5% that are long term successful weight losers regardless of the plan.

  10. Losing weight is not the problem, it’s keeping it off. Over 50 years of medical evidence comes down to only 5% of people being able to maintain weightloss. There is more at work here than people not following diets/ lifestyle change. Hormones like Leptin and Grehlin are working hard to protect us from ‘famine’. Yet again another bad article for people looking for help with obesity. sighs

  11. Your first mistake was reading a Wente column. She is an idiot.

  12. Timothy Caulfield (quoted by Julia Belluz) just appeared in this The Agenda episode earlier this week.

  13. Now I understand why this article category is “Science-ish”. No solid science, but chock-full of assumptions that are not borne out by REAL science. Cherry-picking sources just because you like what they say does not qualify as solid journalism, either.

    Julia, time to start using your head to think rather than as a wind tunnel.

  14. The GI Diet by Dr. Rick Gallop is the only one that has ever worked for me. After reaching my top weight of 285lbs back in 2004, I have been holding stead at 165lbs (120lbs lost) for a couple years now and will never let that happen to me again. No surgery. Just hard work.

  15. The only thing that works for me is keeping a calorie journal; otherwise, even though I don’t have a sweet tooth and eat nothing but home-cooked, healthy food, my portions get progressively larger and larger if I don’t watch out. So I weigh and write down everything I eat before eating it, and when I cook, I add up all the calories of large batches like soup or stew, then calculate how much a portion is, both quantity- and calorie-wise.

    Sunday is my “free” day, and even though I have dessert, potatoes and extra bread (that’s the day I bake my fabulous multigrain loaf), I still write down everything. Sunday is also the day I weigh myself.

    I hate it that food has to be such an obsession, but I’m 70 and I want to continue in good health as long as possible.

  16. WOW!  reading the comments I see there are lot of “experts” out there!  Confusing variety of opinions and advice.  Seems that they are doing exactly the opposite of what the article’s message is – keep it simple.

  17. After reading the article and all the comments, I’d like to add something that so far no one has mentioned.  What about family genetics?  What about your own metabolism?

    Some people are born skinny and can eat a ton and never gain weight.  Whereas some people eat a celery stick and gain weight.  If your family’s history (generations back) are big people, you might be a big person, no matter how much exercise or calorie counting you do.  Same holds true for ones that come from a family of skinny people.

    Put in the mix of both parents where one side is big and the other is skinny, the children can have a mixture as well.  My brothers can eat like horses and never gain weight (my mother’s side of the family), whereas I’m counting calories and go for walks constantly and I’m like my father’s side.

    I’ve always said that no diets work.  You eat what you want (so no chance of feeling deprived and eventually gorge on whatever you love) but in moderation.  Better yet, some even say its better to have 6 little snacks than 3 meals a day.  Others say, eat a big breakfast and reduce your amounts on lunch and even less on supper as you’re not so active in the evenings.  Who the heck knows what works for each person.   We’re all individuals, not part of a borg or clones.

  18. Here’s what isn’t controversial: vegetables, fruit, whole grains, legumes, and water are good for you. So is exercise. 

    If you either mostly or only eat those things, and you exercise, you’ve done your bit. All that’s left is a) accepting what you can’t control in nature and b) accepting and being proud of your body type, however it turns out after eating healthfully (which is really a subset of (a)). 

  19. The Nature of Things just aired a program dealing with chemicals in our food sources and environment that may be directly contributing to disrupting the hormones that control hunger, fat storage, susceptibility to diabetes and weight gain. They call these Obesegens.
    This means that watching your diet and exercise are even more important than ever, but how do we control the levels of these toxic chemicals in our environment when the (various) government(s) allows chemicals to be approved and used before their full potential harm to individuals can be established?
    These hormone disrupters are in our food, the containers they are stored in/sold in, in the sprays that go on our fruits and vegetables, and in the animals we consume.
    It doesn’t let proper diet and exercise off the hook, but this new science may point to the reason that although I have been diligently dieting and exercising over the past 6 months, I have still managed to gain weight.
    It’s hard to close the barn door after the horse has already left.

  20. As far as articles on lifestyle modification and eating habits are concerned, you’ll find far more in-depth references and advice at Mercola.com
    Simply cutting calories results in metabolic stasis after a very short period of time.
    Read Orthomolecular and holistic medical journals. This type of blog is a waste of time.

  21. Go ahead, diet, then put it back on because the problem is much more complex than calories in / calories out.
    The endocrine system is responsible for making us seek food, and making us stop eating food. The food industry adds endocrine disruptors to the food chain, through additives like MSG, hydrolized vegtable protien, and even the chemicals used in plastice packaging (bisphenol “A”). These chemicals turn the “eat” switch on, and keep it on, even after or stomach is full..
    Until we can secure food free form these “disruptors”, dieters will continue to “yo yo” out of control.

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