How many kinds of weight-loss diets are there? Believe it or not, in December 2021, Parade Magazine published an article on “100 Types of Diets That Could Help You Lose Weight.” That’s an awful lot to read about, much less choose from.
But it’s true that some weight-loss diets are better than others. A problem is that not a lot of bona fide, peer-reviewed, professional medical studies published in scientific journals have surveyed this massive field of information. Recently, however, an “umbrella review” of some high-profile diets appeared in JAMA Network Open, a medical journal published by the American Medical Association. The research team was led by Nathorn Chaiyakunapruk, PhD, of the College of Pharmacy at the University of Utah.
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The new research paper did not report on diet experiments conducted personally by the authors but instead surveyed previously published studies on weight loss. The researchers were specifically interested in studying the effectiveness of the diet strategy known as intermittent fasting, or IF. To do that, they identified 11 “meta-analyses” of a total of 130 randomized clinical trials (RCTs) of IF.
“Intermittent fasting,” as the term suggests, is a dietary scheme that involves periods of not eating or eating little. The researchers identified four types of IF:
- Zero-calorie alternate-day fasting (zero-calorie ADF). This involves alternating days of complete fasting (zero caloric intake) and normal eating (what the researchers call “ad libitum eating,” which basically means eating when you’re hungry and stopping when you’re full).
- Modified alternate-day fasting (MADF), which means alternating between ad libitum eating and fasting days of 0 to 600 calories per day.
- The 5:2 diet, in which dieters fast for two days per week (0 to 600 calories per day) and do ad libitum eating for the other five days.
- Time-restricted eating (TRE), which means fasting for 12 to 24 hours per day.
They extracted their data from three authoritative medical databases and rated the studies based on strength of evidence (high, moderate, low, and very low). To be included, the studies had to be analyses of RCTs that investigated associations of intermittent fasting with “obesity-related health outcomes among adults.” They identified 104 reported associations between intermittent fasting and a variety of measures, such as body-mass index (BMI, a measure of weight that takes height into account), body weight, fat mass, hip circumference, and waist circumference.
Benefits found from intermittent fasting
Most of the associations, the researchers judged, were supported by “very low” evidence strength. But they did find 28 associations that were “statistically significant.” These associations, they determined, “mostly involved adults with overweight or obesity.” The evidence demonstrated positive relationships between intermittent fasting and BMI, body weight, fat mass, LDL cholesterol (often called “bad cholesterol”), total cholesterol, triglycerides, blood sugar, blood pressure, insulin, and insulin resistance (HOMA-IR). However, not all the intermittent fasting diets were the same. According to their analyses, modified alternate-day fasting (MADF) and the 5:2 diet “were the only IF types that were associated with statistically significant weight loss of more than 5% in adults with overweight or obesity.” The researchers added, however, that these diets were most effective in the first one to six months. After that, dieters frequently reached a plateau and didn’t lose more weight. The researchers gave two explanations for this plateau. First, the dieters’ bodies made a “metabolic adaptation” to the decreased food intake. And second, the subjects stopped faithfully following the diet plan — a scenario familiar to a lot of people who try to lose weight.
Want to learn more about weight management? Read “Tried and True Weight-Loss Techniques,” “Losing Weight Without Feeling Hungry: Eight Tips,” and “Seven Ways to Lose Weight.”