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The Low-Fat vs. Low-Carb Diet Debate Has a New Answer

Aug 29, 2017
TIME Health
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If there’s one message that most people get about their diet, it’s to cut back on fat. Too much fat, especially the saturated fat and cholesterol found in animal meat, dairy products and cheese, can clog up arteries and lead to heart disease, stroke and obesity.

But fat may not be only culprit in those unhealthy conditions. In recent years, studies have revealed that cutting back on fat doesn’t always contribute to a lower risk of heart disease or reduced chance of dying early. In fact, some studies show the opposite, that people who eat extremely low amounts of fat tend to die earlier.

MORE: Does a Low-Carb Diet Really Beat Low-Fat?

That may be because of something else they’re eating instead. In one of the most comprehensive studies to date looking at how diet affects health and mortality, researchers led by a team at McMaster University report that rather than lowering fat, more people might benefit from lowering the amount of carbohydrates they eat. In a study published in the Lancet, they found that people eating high quantities of carbohydrates, which are found in breads and rice, had a nearly 30% higher risk of dying during the study than people eating a low-carb diet. And people eating high-fat diets had a 23% lower chance of dying during the study’s seven years of follow-up compared to people who ate less fat.

The results, say the authors, point to the fact that rather than focusing on fat, health experts should be advising people to lower the amount of carbohydrates they eat. In the study, which involved 135,000 people from 18 different countries, the average diet was made up of 61% carbohydrates, 23% fat and 15% protein. In some countries, like China, south Asia and Africa, however, the amount of carbohydrates in the diet was much higher, at 63% to 67%. More than half of the people in the study consumed high-carbohydrate diets.

MORE: Know Right Now: Why Low-Fat Diets Might Not Solve Your Health Problems

The findings add more data to the continuing debate over the best advice for healthy eating. When the focus on cholesterol emerged in the 1970s, connecting fatty foods and heart disease, doctors urged people to reduce the fat in their diet by cutting back on red meat, dairy products, eggs and fried foods. Food makers took up the mantra, and pumped out products low in fat. But they replaced the fat with carbohydrates, which scientists now understand may be just as unhealthy, if not more so, than fat.

That’s because carbohydrates are easily stored as glucose in the body, and they can raise blood sugar levels, contributing to obesity and diabetes — both of which are also risk factors for heart disease.

MORE: The Case for Whole Milk

So why has there been so much focus on fat? The researchers say that the first studies to link fat to heart disease were conducted primarily in North America and Europe, which has the highest consumption of fat worldwide. It’s possible that different diet advice may be needed for different populations. In western cultures, where there is an excess of fat, reducing fat may play a role in lowering heart disease, as long as people aren’t replacing the fat with carbohydrates.

MORE: Ending the War on Fat

In other parts of the world, where carbohydrates make up a large part of the diet, cutting back on carbs may make more sense than focusing on fat. “Individuals with high carbohydrate intake might benefit from a reduction in carbohydrate intake and an increase in the consumption of fats,” the study authors write.

More study will also be needed to figure out exactly how much fat and how much carbohydrates should be recommended for optimal health. The study did not compare, for example, people who ate low-fat diets to those who ate low-carb diets to see how their diets affected their mortality.

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