23andMe Wants To Tell You How To Lose Weight

The quest to figure out the right diet for maintaining an optimal weight is often less a quest and more a life-long battle. We cycle through fad diet after fad diet, hoping to eventually one day strike diet gold. Now, the consumer DNA testing company 23andMe is hoping to cut out some of the mystery of dieting, providing consumers with personalised weight loss advice as part of its genetic reports.

Today, 23andMe is kicking off a massive study into the genetics of weight loss that the company says will involve 100,000 people crowdsourced from its database of 1.3 million of its customers. It's perhaps the most ambitious undertaking today date to discern the link between people's DNA and their success at dieting.

For 12 weeks starting today, the company is randomly assigning people to one of three diet and exercise plans, then asking them to report back on how they fared. 23andMe will then parse all that data, hoping to glean information from it that will shed light on the links between our DNA and our success at diets, ultimately incorporating that information into consumer DNA reports.

But before you get your hopes up, it's unlikely that finding the perfect diet will be as easy as forking over $200 and spitting in a test tube - at least not any time soon.

"There have been a lot of claims floating around linking genetics to weight and your perfect diet," Liana Del Gobbo, 23andMe's lead scientist on the study, told Gizmodo. "That science is still in its infancy."

The popularity of consumer DNA testing has spawned dozens of tests that purport to give customers precise information on what to eat and how to exercise to attain perfect health. Those services, though, are mostly bogus, extrapolating, say, from a study of just 68 non-smoking men that drinking 750ml of cloudy apple juice a day will aid in fat loss.

Genetics is a probabilistic science: Whether or not you have a gene related to obesity doesn't mean you're obese, it just means you might have a greater chance of being obese that other people with that gene. Not to mention that often more than one gene is responsible for any one trait. That makes it hard to extrapolate precise - or even remotely meaningful - dieting advice from your genes, and it's basically impossible to do so from smaller studies. Even in a study of 100,000 people, Del Gobbo said it's likely that guidance 23andMe will be able to offer will be very broad.

"We will probably see things like if you are a woman in a certain age bracket with certain genetics you tend to do better on diet A versus diet B," she said. "There's still huge amounts of variation in people in terms of their weight loss success. Is it genetic? Are there other factors? We will start to elucidate some signs, but we plan to be conservative."

Your genes are definitely a part of what impacts your weight, and what works to keep it in check. 23andMe isn't alone in its effort to figure out how it all connects. In 2016, an NIH working group on obesity called for more emphasis on what it called "precision weight loss" through techniques like genetic analysis to improve the success of diets.

"Emerging evidence indicates that genetic variation may impact the efficacy of behavioural weight loss interventions," the working group wrote.

Large scale, genome-wide association studies like 23andMe's have thus far identified over 150 genetic variants associated with weight. But a far smaller number of genes have been associated with body weight change. What we know at this point is, essentially, that genetically personalised diets could totally one day be a thing, but first we need a lot more really big studies to better understand gene — diet interactions.

23andMe has long sent health surveys to its customers, but beginning last May it started looking at whether it might also be able to enlist them as subjects in research studies. First, it conducted a pain-tolerance experiment, asking customers to test how long they could keep a hand in a bowl of ice water. Then it conducted a sleep study, asking 6,000 volunteers to change their behaviour and see how it affected their sleep. 23andMe's research follows much of the same protocols any academic study would, including getting approval from an independent ethics board.

In the weight loss study, 23andMe will randomly assign people to one of three plans. In some cases, participants will be asked to avoid carbs like bread. Another group will try eating more fibre and less animal fat. A third will eat as they usually do but exercise more. Other factors besides genetics, of course, also influence diet success, so participants will report back on things like their levels of stress and whether they had "cravings," along with whether or not they lost any weight.

23andMe already gives customers a report that tells them whether their genes indicate a tendency to be heavier or thinner. The new study, the company hopes, will make that information more useful, figuring out which genes or other factors play a role in who lost weight and who gained it.

"Do I think we're going to find dozens and dozens of robust hits on our first try? Perhaps not," said Del Gobbo. "We can't at this stage make very many if any firm conclusions."

But the important thing, she said, is that studies are getting larger, more frequent, and more comprehensive.

23andMe's study is many times larger that other studies that have looked at this question, the largest of which looked at a few thousand people. Having access to a database of over a million people is a pretty good way to get a large sample size.

"To understand behavioural weight loss you need huge numbers," Del Gobbo. "Before working at 23andMe, I dreamed of doing a study this big and could never do it."

You may one day be able to spit in a tube and get a customised weight-loss plan, but it's not yet possible - so be wary of any company peddling genetically tailored diet advice.

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