Atkins, Keto, South Beach? Choosing the best weight-loss method can be overwhelming. If we learn to cut through the hype, we can narrow down our options by looking at only the medical weight-loss studies that are relevant to us.
What Medical Studies Should You Take Seriously?
About 50,000 scientific studies are published per week just in the English language. Not all of these, or even most of these, are relevant to most people.
To help determine if a study is salient to you, ask yourself these questions: Is this study about people like me, and is the endpoint, the thing they’re measuring in the study, something that’s important to my health?
Let’s look at two headlines about two recent studies, and see if they pass the salient tests.
From the UK, we have the headline, “THIS Vegetable Could Be the Key to Preventing Obesity as You Age.” Referring to metabolism, the article says that “Research has found an extract in red hot peppers that may speed [metabolism] up as you get older, and, therefore, help you ward off obesity.”
Metabolism was increased to the equivalent of burning an extra 116 calories a day, which would mean, the article says, a pound of fat lost over 30 days. Wow. That sounds pretty good, right?
This is a transcript from the video series The Skeptic’s Guide to Health, Medicine, and the Media. Watch it now, on The Great Courses Plus.
But let’s look closer. First, who were the subjects, and were they like me or you?
The subjects included 40 healthy adults, ages 22 to 47, a mix of men and women, of about average weight. That group of people may mean that these results would be less applicable to people who are overweight, or people much older than 47.
The next question is about the endpoint: What was measured and is it important to me? The news article talked about the metabolic rate and said the findings suggested that red pepper extract would lead to a weight loss of a pound of fat over 30 days.
But that’s not what the paper itself said. The investigators used a measure of metabolic rate over three hours and didn’t measure weights.
We don’t know if that metabolic change would be sustained over 24 hours, much less over a month. That business about metabolic rates leading to weight loss is smoke and mirrors.
The authors jumped from metabolic rates to weight loss, a conclusion based on 50-year-old data that led to the so-called 3,500 calorie rule—3,500 calories lacking equals one pound of weight loss, and 3,500 calories extra lead to one pound of weight gain.
This data was from very short-term experiments on a small number of men who had been fed a severely calorie-restricted diet of 800 calories a day.
More recent research—and this should have been well-known to the authors—has shown that metabolic changes are rapidly compensated and that projected weight losses based on metabolism, in practice, are often one-tenth or less than what would be predicted by this 3,500-calorie rule.
The study reported here fails the “Is the endpoint important to me?” rule. It wasn’t about weight management or weight loss; it was about measuring metabolic rates. The article connected the data to weight loss, but it did a poor job doing that, creating a misleading story.
The study’s authors also were employed by a company that makes and sells a hot pepper extract. That fact doesn’t automatically mean that the results should be dismissed, but it should certainly raise your skepticism.
Look at where a study comes from, who did it, and who paid for it before you decide just how seriously you’ll take the results.
Looking Deeper at a Weight-Loss Article
Consider another news story about a study from The Washington Post, this time: “New Drug Tricks Metabolism into Burning Fat as if You’ve Just Finished a Meal.”
There’s a very typical photo at the top of the page of an overweight individual shown from the ankles up to the neck, with no view of the head. One blogger refers to these types of photos as “headless fatties.”
The article starts, “Experts rightfully caution against relying on miracle diet drugs…” Okay, good start. Then, “A new study offers a novel approach that bears watching.”
The article continues by saying that researchers developed a compound that “tricks the metabolism into responding as if a meal has been eaten, causing it to burn fat.” Better yet, the article goes on to say, the new compound is “much safer than” other existing drugs.
Noteworthy, though, The Washington Post then does address one of our questions of salience, though it’s buried under the lead. About halfway down the page, it is mentioned that the study was done on mice, and that primate studies will also be needed before potential human trials years down the road.
In answer to our question, is the study about me? No, unless you’re a mouse.
But the headline is misleading—the headline was “New Drug Tricks Metabolism into Burning Fat as if You’ve Just Finished a Meal,” not “as if a mouse just finished a meal.” Studies in lab animals are hugely important and give us very valuable information.
But very few compounds studied in animals ever make it to become human medicine. It’s a starting point, but it’s not likely to lead to anything you can use or any medicine you can take, at least not anytime soon.
There’s also the safety angle here. The Washington Post article said that the new compound would be safer than existing medications, but it wasn’t compared to any existing medicines, and it wasn’t even given to people.
It’s a huge stretch to go from a trial studying effects in mice to declare that a medicine is safe for humans. Be wary of conclusions when they haven’t been directly and objectively measured on people in a cohort study that would resemble your own specifics.
What about the other test of salience—are the results important to me? The study showed a reduced weight gain in the treated mice—an important endpoint to measure, maybe the most important.
There were other measured endpoints as well, including measurements of inflammation and metabolism. These other endpoints contributed to the headline focusing on “tricking the metabolism into burning fat.”
The headline is meant to be more attention-grabbing than just talking about mice losing weight. People seem to like the idea of a trick, or a kind of an easy way, to burn fat. But, again, it will be a long time, if ever, before this medication is shown to be safe and effective for human use.
What IS the Most Effective Diet?
Let’s answer a question that is likely on many people’s minds: What is the best diet to follow if you want to lose weight or maintain a healthy weight?
The headlines are all over the place. You’ll read about low-fat, or low-carb, or paleo, or more-specific named diets like Atkins, South Beach, or Weight Watchers.
Some of these are more than diets, and include healthful lifestyle changes, too, but we’ll just concentrate here on what people eat. Beyond the advertisements, the bestseller lists, and the headlines, what’s the more effective diet out there?
In 2009, the Pounds Lost study was published—the first word of the name stands for Preventing Overweight Using Novel Dietary Strategies. Good studies often have clever abbreviations like that.
This looked at four different diets that differed in the percentage of calories from fat, carbohydrates, and protein. After two years—that’s a good, long follow up—people in all four groups had all lost a similar, modest amount of weight, and all four groups ended up about the same in terms of both weight loss and changes in body fat and lean mass.
A few years later, a 2014 meta-analysis combined the findings from all of the published literature comparing different dietary approaches and came to the same conclusion—that any diet that reduced calories, either by reducing fat or carbohydrate calories, was just as likely to work.
The answer is simple and not one to grab attention in any headline: Any diet can work. The trick isn’t picking the diet; it’s sticking with the diet.
People interested in weight loss should not even think about eating in terms of a diet. Saying that you’re “going on a diet” implies that “a diet” is a temporary thing—something you go on, and will probably go off.
Learn more about how to think like a skeptic when reading news in any medium
It’s better to make small changes that can be continued for life than to make big changes that will last only a few, discouraging weeks.