The one thing you need to know about weight loss and diet studies

Another day, another diet study, this latest demonstrating once again that all diets perform about the same.

Examining the best-available studies about Atkins, Weight Watchers, and Zone diets, researchers publishing in the journal Circulation found that people tended to lose about five or seven pounds over the course of a year, then re-gain some of that weight in the long term.

They also found that — notwithstanding all the claims of superiority these programs make — a lot of the evidence on branded diets was so low quality and short term, it was hard to truly know which one worked best.

"Despite their popularity and important contributions to the multi-million dollar weight loss industry," said Mark J. Eisenberg, one of the study's authors, in a press release, "we still do not know if these diets are effective to help people lose weight and decrease their risk factors for heart disease."

This latest bit of research follows a big JAMA review from September that also found that all diets — low fat, low carb — have about the same modest results, no matter their macronutrient compositions.

The one thing you need to know about weight loss

Before you get dispirited by this news or bogged down in the latest finding — and I'm writing this up top because I don't want you to miss it — if you take one thing away from this article about weight loss it's this: there is no magic diet, no belly blaster or flab fighter, no weight loss wonder, or thinning superfood.

You can ignore the noise, the hype, the branding, the celebrity-endorsed diet books, and the Dr. Oz-backed metabolism boosting miracles in a bottle. You can even ignore the contradictory studies that come out every few months.

The one thing you need to know from science about dieting is rather straightforward. What works is cutting calories in a way that you like and can sustain. That's it. Fewer calories means more weight loss. It's really that simple. You can stop reading here if you want.

Why studying diet is almost as difficult as losing weight

Studying diet is difficult, which is why many researchers — including the authors of the newest diet study — often conclude that the evidence out there is very low quality.

Consider this: if you stick people in a lab and carefully measure everything they eat, you'll get an accurate picture of what went into their bodies, but the results won't reflect what goes on in the real world. If you set participants loose and ask them to report back on their calorie intake with little monitoring, you'll still get an inaccurate view because people are notoriously bad at remembering what they ate and frequently underestimate their calorie consumption.

Studying diet is also really expensive. So studies tend to be short term, and again not reflective of real-world outcomes. And we know most people, sadly, regain the weight they lose after a while, so in order to understand whether a diet truly works, a study needs to run for more than a year... and it's therefore more expensive and difficult to fund.

The Mediterranean diet. (Photo courtesy of Universal Images Group)

Culture matters, too. This classic study of weight loss comparing low-carb, low-fat and Mediterranean diets found that the low-fat group had less success than the others. The study took place in Israel, Harvard's Dr. Frank Sacks told Vox. "In Israel, people eat more of a Mediterranean-style diet to begin with, so I think that people's customs — what they like to eat — had a lot to do with the success of any particular diet advice."

Remind me: what diet really works?

Well, I told you already. But if you read this far, I'll reward you with a few easy and evidence-based ways to cut calories: eat fewer restaurant meals and stop drinking sugar-sweetened beverages.

We also know that people who track their calories and regularly weigh themselves lose more weight than people who don't.

Dr. Yoni Freedhoff, an Ottawa-based obesity doctor — who has worked with thousands of overweight and obese patients — says he tells people, "Ultimately you need to like the life you're living food-wise if you're going to keep living that way. It's crazy to think, with billions of people on the planet, that there's one approach that suits everybody." He added: "The best diet for one individual is the worst diet for another individual."

In his book the Diet Fix, he reccommends tracking what you're eating for a few days to see where you're getting most of your calories and where you're tripping up, and then taking a hard and honest look at that information to figure out where you can reasonably cut back without hating your life.

Tim Caulfield, author of the Cure for Everything, is also excellent on the question of  how to diet. He writes: "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."

Never want to see another diet study again?

Julia Belluz on Dr. Oz's big weight-loss lies (and one truth).

You're not alone. Even the diet gurus are fed up. Harvard's Dr. Frank Sacks said he's "dispirited about all these crazes going back and forth" with different diets coming in and out of fashion every few years. Stanford's Christopher Gardner also said these studies that focus on "the best diet" are mostly a waste of time since they're usually so low quality, they don't tell us much anyway.

"It's the wrong question," he added. "The better question now should be 'what is the best diet for different individuals, and how can we match them to those diets?'" To understand this, Gardner said researchers would need to look at people's behaviors, microbiomes and genetic makeup, and how they respond to particular diets. Until science reveals this more refined picture, remember Caulfield: simplicity is the revelation.