Dieting Theories Updated

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By Mary Carpenter

DIETARY recommendations seem to change so often it can be hard to keep track of which ones, such as the currently popular intermittent fasting, are backed by high-quality evidence. In the past week, for example, the Washington Post highlighted two surprising or unfamiliar dietary reports — one, that previously villainized cheese may be protective against cardiovascular disease and type 2 diabetes.

The second is that the USDA’s MyPlate nutrition guidelines, which replaced the food pyramid in 2011, remains unfamiliar to 75% of Americans and affects daily diets of fewer than 10% of adults. On the other hand, people are becoming more aware of the benefits of tailoring diets to individual needs, as well as general advice for those over age 50 to up their daily consumption of protein.

That “obesity is not a personal failing” may, however, remain the most difficult nutrition-related concept for Americans to accept. Writes Julia Belluz in a New York Times editorial describing the recent three-day London conference of obesity researchers: “No presenter argued that humans collectively lost will power around the 1980s, when obesity rates took off…in much of the world. Not a single scientist said our genes changed in that time.”

“All the carbohydrates and fat in our food today dilute the protein our bodies need, driving us to eat more calories to make up for the discrepancy,” proposed one presenter. Echoed another: “eating patterns heavy in carbohydrates are uniquely fat promoting.” Some experts mentioned potential contributions of ultraprocessed foods and the toxic substances they may contain. With more than a thousand genes and variants discovered that increase a person’s obesity risk, conferees agreed: “As long as we treat obesity as a personal responsibility issue, its prevalence is unlikely to decline.”

The popularity of intermittent fasting (IF)—limits on eating to windows of time within each day of 12 hours or less, or one or more days each week—comes from its focus on when to eat rather than what, making IF easier to follow for both weight loss and improved health. By contrast, alternatives such as calorie-restriction diets have a high dropout rate, while the best research-supported diets for health benefits—notably the Mediterranean diet—require keeping track of a variety of food choices.

“The hypothesis behind time-restricted eating is that circadian genes that are thought to increase metabolism are turned on during daylight hours,” Wellness and Weight- Management Co-Director at Brigham and Women’s Hospital in Boston, Caroline Apovian, told New York Times (NYT) writer Gina Kolata. But the most recent research found that time restrictions produced no improvement in “such risk factors as blood glucose levels, sensitivity to insulin, blood lipids or blood pressure.”

In the study of 139 women with obesity, all on low-calorie diets of 1,200 to 1,500 calories a day, half restricted their eating to an eight-hour window between 8am and 4pm while the others did not—with no significant difference between the groups in either weight-loss amount or risk factors. According to UCSF diet researcher Ethan Weiss, “these results indicate that caloric intake restrictions explained most of the beneficial effects.”

Limiting hours of eating may still, however, be the best way for many people to restrict the total number of calories they consume. What may be less well known is the “typically high dropout rate in weight loss studies using IF,” according to Colorado State University food sciences writer Eliza Venetis, “which demonstrates how hard it is to stick to IF in the long run.”

For individuals unable to lose weight with diet, a recent alternative is drugs approved for specific diseases like diabetes. One drug, semaglutide, has different brand names—as well as price tags and insurance coverage—to enable its marketing for either diabetes or weight loss. And the diabetes drug metformin has helped with weight loss and may also slow aging.

MyPlate recommendations emerged from years and millions of dollars spent on research. Despite poor promotion, the general recommendations from MyPlate are better known: Consume about half of daily food in fruits and vegetables; and eat fewer carbohydrates and more fats—notably more unsaturated fats, such as nuts, seeds and fatty fish like salmon.

Increasing daily protein intake, meanwhile, has been garnering more support, especially for those over 50—and especially during stressful periods when “aging bodies process protein less efficiently,” writes Judith Graham for Kaiser Health News. Graham cites a 23-year study showing “older adults who consume more protein are less likely to lose functioning,” and she recommends animal protein that “contains all nine essential amino acids that our bodies need”—but admits that, with a little effort, these can be obtained from plant protein as well.

Eat 30 to 45 grams of both protein and “total carbs” per meal to stave off muscle loss is the AARP recommendation from a series of articles—and consume protein early in the day. From the AARP-published The Whole Body Reset by Stephen Perrine: “Studies show that older folk who fail to get 25 to 30 grams of protein in the morning are likely to stay in muscle-loss mode all day.” Other recommendations include strength-training and eating lots of fruits and vegetables.

Misinformation extends to all consumption, such as the goal of drinking eight glasses of water a day. Updated advice is to drink water when you’re thirsty, and it’s better to do so before or after meals versus while eating when water can dilute digestive juices. Drinking water can, however, can help prevent stomach growling. The misperception is that hunger is the cause, whereas such rumbling or gurgling noise is a sign of digestion underway.

And as for cheese, studies on health benefits have upended earlier blame for coronary vascular disease (CVD) on saturated fats. According to a 2019 University of Copenhagen study of 136,384 individuals from five continents, the results “clearly demonstrated that dairy consumption…is associated with lower risk of mortality and major CVD events.”

“Body neutrality” —accepting and respecting different kinds of bodies—might be the most important nutrition goal for the future, based on the obesity conferees’ conclusion that as long as “the individual choice bias dominates…fat shaming promotes weight gain and harms. At least some of obesity’s negative health consequences are thought to be driven by stigma and discrimination which results in poorer health care.”

Growing up with a grandmother who praised “eating to live” versus “living to eat,” I developed the knee-jerk reaction of criticizing heavier bodies—along with the flip side, commenting positively when someone appeared to have lost weight. While working on “body neutrality,” I am trying to figure out how to squeeze the many MyPlate recommendations into daily consumption—as well as how to eat more protein, especially at breakfast time.

—Mary Carpenter regularly reports on need-to-know topics in health and medicine.