This article originally appeared in the Winter 2019 issue of Tufts Nutrition Magazine.
Lulu Hunt Peters never managed to become a household name. But the weight-loss method she unleashed upon our culture a century ago—counting calories—has more than made up for that. “Hereafter you are going to eat calories of food,” the California physician ordered readers of her 1918 guide Diet and Health. “Instead of saying one slice of bread, or a piece of pie, you will say one hundred calories of bread, 350 calories of pie.” Watch a supermarket shopper study the top of the Nutrition Facts panel, and you’re looking at Lulu Hunt Peters’s legacy.
Scores of weight-loss schemes have come and gone in the hundred years since Diet and Health became the first dieting book to hit best-seller lists. But at the heart of a great many of them was the idea of keeping obsessive track of calories to cut pounds. The idea endures today. Rather than follow “trendy, nationally advertised diets,” wrote a contributor to a January 2018 Journal of the American Medical Association, an issue dedicated to the subject of obesity, “it is better for physicians to advise patients to assess and then modify their current eating habits and then reduce their caloric ingestion by counting calories.”
And yet. Diet veterans can tell you that successful, long-term weight loss often seems to elude a simple “calories in/calories out” formula. Many nutrition experts agree. A growing body of scientific evidence, while still highly controversial, suggests that a focus on calories should be dropped altogether. “In the short term, calorie counting works great,” said Dariush Mozaffarian, dean of the Friedman School of Nutrition Science and Policy at Tufts. “If you reduce your calories, whatever the composition of your diet, you will lose weight for a few months. That’s why all fad diets work initially.” But eventually, the body will fight back and the weight will return.
Consider the experience of Julia Kozlov, a Southern California finance executive with two teenagers at home, who started using one of the popular calorie-counting smartphone apps in 2017. When her job found her trapped at her desk with the stress of month-end closings, she’d eat random combinations of foods. It didn’t matter what they were, just as long as they fit under her calorie cap—a number she watched with single-minded devotion. “It was the hardest thing to be counting all those calories,” she recalled. “I created a spreadsheet. I drove myself insane.”
So how to untangle the complicated relationship between food intake, nutrition, health, physiology, metabolism, and weight loss? Finding a way is more urgent than ever.
Despite all her hard work, Kozlov ended up gaining ten pounds in about seven months, a turn of events that left her frustrated and seriously worried. At one point, she was so concerned about her health that she actually made an appointment to see her doctor. “Am I going through perimenopause? Do I have a thyroid issue?” she asked. “Is there something wrong with me?”
With forty-five million Americans embarking on diets every year, a lot of us are asking ourselves the very same question. Two out of three adults in the United States meet the clinical definition for being overweight or obese, a figure that has more than doubled in the last half-century. Treating the chronic diseases that arise from the obesity epidemic, especially Type 2 diabetes and cardiovascular and circulatory conditions, are costing the United States upwards of $147 billion every year. By comparison, the annual budgets of the National Institutes of Health, the Centers for Disease Control and Prevention, and the Food and Drug Administration are only about $53 billion combined. So how to untangle the complicated relationship between food intake, nutrition, health, physiology, metabolism, and weight loss? Finding a way is more urgent than ever.
Every day at Tufts Medical Center, Jillian Reece sees people whose health depends on their losing weight and keeping it off. A registered dietitian, she counsels patients at the hospital’s Weight and Wellness Center. Some come for short-term consultations, others undergo medical or surgical interventions. Almost all of them have a Body Mass Index (BMI) of at least twenty-five, making them clinically overweight, and most meet the definition of obese.
When they first come in, many of Reece’s patients don’t know where to begin to navigate the confusing thicket of weight-loss advice they’ve encountered over the years. So they often end up falling back on something that seems to make sense: calorie counting. “The question we get a lot is, ‘How many calories should I be looking at, can you give me an estimate, a number?’” Reece said. After all, the 2015-2020 Dietary Guidelines for Americans advises that to lose weight most women should cap their daily calories at 1,200 to 1,500, and most men at 1,500 to 1,800. Although people will press for numbers, Reece said, they are a “very simple way to answer a very complex question.”
The problem, Mozaffarian said, is that the formula of “calories in/calories out” is “grossly oversimplified.” It supposes that each human body is like a bucket that gets filled with calories at the top and emptied of calories at the bottom. That isn’t what happens at all. “Food does not merely represent calories. Rather, food represents information, signals that influence and interact with multiple complex biologic pathways in our bodies,” he said. “And, long-term, the effects of a food on these pathways, rather than the calories in that food, are what controls our weight.”
Calorie for calorie, different foods have varying effects on important pathways throughout our body, including those related to our brain, liver, insulin and other hormone responses, fat cells, and gut microbiome. Growing research indicates that different foods even influence our metabolic rate—the amount of energy we expend. From these effects, the various foods we eat, even if they have similar caloric values, can in the long term make it easier or harder for our body to regulate our hunger, fullness, unconscious cravings, and metabolism and maintain a healthy weight.
The gut microbiome—the community of bacteria in our large intestine—appears to be especially important. While two foods can have the same calories, the calories may be distributed in different ways to the cells of the body than they are to the cells of bacteria in the gut. For example, starch in a refined grain (like white bread and most breakfast cereals) is fully digested in the stomach and small intestine, with few if any of its calories reaching the bacteria in the large intestine. In contrast, starch in a partly intact whole grain like steel-cut oats—or in minimally processed food like beans or vegetables—is protected from digestive enzymes by the food’s fiber structure. So the undigested starch (and its calories) may reach the large intestine, where it can feed our gut bacteria. The body’s total use of calories is the same in most cases, but the calories are divvied up differently.
Faced with that kind of complexity, it’s hard to come up with a single “golden rule” for reaching a healthy weight. For instance, for decades, all fats as a group were viewed as the villain of the American diet. But research by Mozaffarian and others has shown that characterization was a mistake. Meanwhile, many of today’s popular catchphrases—“low-carb,” “plant-based,” “vegetarian”—all have a tendency to be misleading because they can be too simple and narrowly interpreted. “One of the unfortunate truths,” Mozaffarian said, “is that there is no easy, one-word description of a healthy diet.”
‘What really drives long-term success’ is not
strictly how many calories we eat. It’s what we eat.
Some ostensibly successful diet programs may also lead to confusion over cause and effect. Look at the low-carb, high-fat Atkins diet, which periodically sees a burst of popularity, and is the forerunner of today’s “keto” and “paleo” crazes. Robert Atkins hypothesized that putting the body into ketogenesis, the process of breaking down stored fat molecules for energy, produced sustainable weight loss. “Atkins was right about the importance of avoiding refined starch and sugar,” Mozaffarian said. “But, all carbs are not harmful. It’s now pretty clear that low doses of slowly digesting carbs, like in fruit, beans, and nonstarchy vegetables, are not a problem. And, simply avoiding refined starch and sugar can lead to substantial weight loss, without activating ketogenesis.” (The Atkins diet has been revised to at least partly incorporate this newest science.)
Which is not to say the Atkins diet hasn’t helped clarify a key lesson: that strict calorie counting is unnecessary. “Where the Atkins diet was correct was to ignore calorie counting. It has no calorie limits,” Mozaffarian said. “And that sort of blows the calorie-counting hypothesis out of the water.” Within the past year, two studies—one published in February 2018 in the Journal of the American Medical Association, another in November 2018 in BMJ—reported significant weight loss in adults who didn’t count calories.
What the participants in those study did do was eat healthy foods. The kind of diet that, as Mozaffarian puts it, “is rich in foods that give rise to life”—foods that grow when you plant them. That means lots of fruits, nuts, seeds, beans, nonstarchy vegetables, and minimally processed whole grains, as well as plant oils extracted from these foods. Fermented foods like yogurt and cheese also appear to provide benefits, he emphasized. And a healthy diet avoids foods rich in refined starch and added sugar, which lead to spikes in blood sugar and insulin.
Look over decades of scientific evidence and one fact becomes clear, Mozaffarian said. “What really drives long-term success” is not strictly how many calories we eat. It’s what we eat.
Rebecca Searl Johnson, a 2007 graduate of Cummings School of Veterinary Medicine at Tufts, has experimented with a number of diets over the years. She first tried Weight Watchers, the grande dame of the weight-loss world, when she was a student and has been on and off the program a few times since. Not long ago, she switched to calorie counting, only to hit a plateau after an initial loss. “I found myself, at the end of the day, really struggling—I think that’s when most people struggle—and I really wanted something to eat,” she said. And when late-day hunger set in, she wouldn’t make the healthiest choices.
Recently, however, Johnson returned to the diet program and noticed some changes. The program, which now has four million members worldwide, rebranded itself in September as WW, taking “weight” out of its name and introducing a new tagline, “Wellness that Works.”
WW, which got its start in 1963, has for the past two decades asked dieters to count “points,” numbers the company assigned to foods based on measures like their calories, saturated fat, carbohydrate, and protein content. But now WW has developed a system that abandons counting altogether for more than two hundred different foods—including most vegetables, fruits, lean protein, and nonfat plain yogurt—that contribute zero points to members’ daily targets. In other words, people can eat as many of them as they want.
“The reason to not count calories is that they tell you nothing about the health or nutrition of a food,” said Gary D. Foster, WW’s chief scientific officer. “Fundamentally, calories are a shallow, hollow, empty metric, if you’re concerned about overall health. Three hundred calories of a nonfat Greek yogurt fruit parfait, or three hundred calories of two chocolate-chip pancakes, are just not the same.”
For many weight-watchers, the introduction of so many zero-point foods—fruit, in particular—upended long-held orthodoxies. But the move, Foster said, was not that revolutionary. The zero-point foods were chosen with two criteria: They are at low risk for overeating—how much skinless chicken breast will one person want to eat, really?—and they form the “foundation for a healthy eating pattern.” For instance, releasing the restrictions on fruit was intended to bolster the woefully small percentage of Americans who eat the recommended daily number of fruits and vegetables.
“We take our responsibility seriously to encourage people to eat healthier, not just to eat fewer calories,” Foster said. “If you only track calories, that’s only half the picture.”
Susan Roberts has spent a lot of time thinking about weight loss. She’s head of the Energy Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, a Friedman School professor, and a professor of psychiatry at Tufts Medical School. She’s published more than two hundred papers on weight loss and developed an online weight-loss program, The “I” Diet, based on the evidence-based idea that people can retrain their brains and adapt their behavior to avoid cravings and overeating. And she’s struggled with her weight herself—gaining fifty pounds after the birth of her daughter, then losing it—so she understands the limitations of a diet focused exclusively on counting calories.
“I think when people say it’s time to stop focusing on calories, what they often mean is that counting calories doesn’t work, and I totally agree with that,” Roberts said. “It’s tedious, inaccurate, and sets you up for failure.”
But at the same time, she argues that the opposite extreme—the instinct to eat as if calories don’t matter—is also doomed to failure. “All weight-loss plans try to get people to eat fewer calories in one way or another,” Roberts said. “Those who are susceptible to weight gain can always eat something. Telling them not to think about calories is just asking for trouble.” (While Roberts and Mozaffarian agree on many aspects of nutrition science, he disagrees with this point—there is remaining controversy among experts about whether calories need to be tracked at all.)
Rather than look at weight loss as a question of calorie counting versus diet composition, Roberts said the goal of a weight-loss program should be to provide support and change behavior, so that people are eating differently and then staying with those new, healthier habits. That’s part of the reason why she developed an online support program to help participants stick with the program she lays out in The “I” Diet. “The proof is in the pudding,” she said. “It all comes down to finding ways to help people reduce what they eat.”
One key way to accomplish that, Reece tells her patients at Tufts Medical Center, is by tackling the problem of portion sizes. When people pop into her office, they often ask if they’re interrupting her lunch. At first glance, the plate of grilled chicken, mashed potatoes, carrots, and broccoli perched on the side of her desk looks pretty tasty—even after you realize it’s all plastic, it still looks kind of appetizing.
The faux food is there to illustrate optimal portion sizes, a challenge in an increasingly supersized food culture. Even when Reece’s patients try to count calories, they often inadvertently low-ball how much they are eating. Sometimes, after they tell her they had three ounces of chicken for dinner, she’ll hold up the three-ounce portion of demonstration chicken—“like this?” she asks. It almost invariably turns out they actually had more like nine ounces, triple the recommended portion—when servings get that large, calories can add up. “Saying calorie counting is dead does not mean the concept of energy balance is dead,” Reece said. “You can keep the total calories down without having to focus on it.”
Counting calories doesn’t work,” Roberts said. “It’s tedious, inaccurate, and sets you up for failure.
Like much of the science on weight control, not every expert agrees about focusing on portion sizes. “If you are eating foods likely to cause weight gain—foods rich in rapidly digesting refined starch and sugar, sugary drinks, or processed meats—then, absolutely, eat as small a portion as possible,” Mozaffarian said. “But, if you’re eating foods that help the body’s usual pathways for weight control, improve metabolism, and augment health—foods like minimally processed fruits, nuts, seeds, beans, nonstarchy vegetables, whole grains, plant oils, yogurt, and perhaps even cheese—there is little evidence that portion control is relevant.”
These days, Julia Kozlov—the finance executive who gained weight by counting calories—is primarily focused on separating the healthy foods from the bad ones. On January 1, 2018, she did what many Americans do on that day: She started a new diet. She dropped her calorie-tracking spreadsheets, her low-calorie snacks and processed foods, and, in ten months, fifteen pounds.
Following the new WW program, Kozlov is eating plenty of chicken, fruits, and vegetables. She’s aware of the calories she’s consuming, but she’s more focused on cultivating new habits that feed into her health. “Today for lunch I had 650 calories, cedar-planked salmon and succotash,” she said. “Sure, I could have eaten something for 300 or 400 calories, but would I have been as full and would it have been as nutritious?”