The study that claimed chocolate helps you lose weight? It’s fake
Published: May 29, 2015
Eat chocolate and lose weight? That’s the best news I’ve heard all day!
Coffee is good for your heart. Red wine helps you live longer. And the latest scientific claim: Chocolate helps you lose weight. One caveat: It’s based on terrible science.
A press release on March 29 made a promise that newspapers and magazines around the world would repeat: “Can you indulge your sweet tooth and lose weight at the same time? If it’s chocolate you crave, then the answer seems to be: yes.” Lead author “Johannes Bohannon,” research director of the nonprofit Institute of Diet and Health, said, “Just lowering the proportion of carbohydrates is not a reliable weight loss intervention because it has different physiological effects depending on the bioactive compounds in your diet.”
Sure, losing weight with the help of a daily dose of chocolate does sound too good to be true…but it seemed scientific. The researchers divided subjects aged 19 to 67 into three groups: One group followed a strict low-carbohydrate diet, another group followed the low-carbohydrate diet and also consumed 42 grams of dark (81%) chocolate per day, and a control group followed their status quo diet. The low-carb group lost weight compared to the control group, but the low-carb plus chocolate group lost 10% more weight. The chocolate group also reported better sleep and well-being, and their blood cholesterol levels were significantly reduced.
Now the reality.
Johannes Bohannon is John Bohannon, a journalist, and the study was actually commissioned by German TV producers making a show about the junk-science diet industry. The Institute of Diet and Health was a website. The study had only 15 participants and included 18 different measurements, including weight, cholesterol, sodium, blood protein levels — a recipe for false positives, Bohannon says. “It was, in fact, a fairly typical study for the field of diet research,” he says. “Which is to say: It was terrible science. The results are meaningless.”
Don’t be fooled by junk-science diet industry
(3:49)A fake study about chocolate and weight loss illustrates the dangers of not looking closely at how studies are conducted.
“Other than those fibs, the study was 100% authentic,” he writes of his exposé. The sloppy science and its appealing conclusions got headlines in the Daily Star, Huffington Post, Irish Examiner, Daily Express and was on the front page of the German tabloid Bild. Subjects in the clinical trial were assigned different diet regimes, and the statistically significant results were based on the actual data. “Here’s a dirty little science secret: If you measure a large number of things about a small number of people, you are almost guaranteed to get a ‘statistically significant’ result.”
The diet industry gulls people into believing that certain products produce weight loss, when even the science shows the opposite, says Gary Ruskin, executive director of U.S. Right to Know, a consumer advocacy group. But he is concerned by the number of studies that suggest surprising ways to lose weight, and says people should read the actual study and, given the infinite amount of variables, take them with a grain of salt. “So many studies are designed to produce a result that is favorable to a manufacturer,” he says. “Science journalism blasts out what food and diet companies say as fact with far too little scrutiny.”
Last June, Mehmet Oz, more commonly known as “Dr. Oz,” appeared before the Senate Commerce, Science and Transportation Committee to defend calling weight-loss products “miracles” or “lightning in a bottle” on his show. The British Medical Journal found that evidence supported just 46% of medical products recommended on his show. (”To not have the conversation about supplements at all however would be a disservice to the viewer,” Oz said in a prepared statement after appearing at the hearing. He also told Congress he had used “very passionate” language that “provided fodder for unscrupulous advertisers.”)
Headlines often don’t tell the full story. This 2010 Reuters headline “Wine may help women keep weight in check” was based on a study in the JAMA Internal Medicine, a peer-reviewed medical journal published by the American Medical Association. One caveat: The women who consumed more alcohol also ate fewer carbohydrates. And this Daily Telegraph headline, “Glass of wine with dinner helps you live longer,” was based on a 2014 Czech study, presented at the European Society of Cardiology Congress in Barcelona. The results were only positive in those who exercised.
And this recent headline, “Another reason to drink coffee: It’s good for your heart, study says” in the Los Angeles Times was drawn from a study of over 28,000 men and women published in the journal Heart, the official journal of the British Cardiovascular Society. “Moderate coffee consumption was associated with a lower prevalence of subclinical coronary atherosclerosis,” it found. Like all studies, the results show a correlation — not a causation — and drinking more than five cups of coffee a day was associated with higher levels of coronary atherosclerosis, a bad end result for coffee addicts.