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Humans have been trying to lose weight since as far back as the third century B.C., when Hippocrates advised patients to stay slim by eating light foods, using seawater enemas and wrestling. Diet crazes, exercise fads and other dubious practices in the name of weight loss have been going strong ever since.

In the 11th century, William the Conqueror invented the all-liquid diet after he got too fat to ride his horse. (The diet failed and some time later he fell off his horse — a tumble attributed to his corpulence — and died.)

Nineteenth-century poet Lord Byron was famously afraid of gaining weight. He spent days eating nothing but red cabbage and apple cider vinegar — and exercising while wearing as many as six coats, to better sweat out water weight.

Recent decades have been no different. We’ve cycled through the grapefruit diet, cabbage soup, cookies crammed full of wheat germ and low-fat everything. Today, you’re apt to hear that the only path to sustainable weight loss is to eat nothing but fat.

But what does sustainable weight loss look like if we peer beyond the fads and gimmicks? What does it take to lose weight and keep it off?

Experts eschew quick fixes; they believe that the path to a lean physique is the same as the path to vibrant health. Weight that comes off and stays off involves changes in more than just food and exercise. This shift sets today’s approach to sustainable weight loss apart from past protocols. We asked three local experts to weigh in on the new thinking around weight loss.

Food

What, how much and when we eat are among the biggest factors in the weight-loss matrix — and there’s one golden rule that almost all experts agree on: eat whole, real food.

“It’s like [food writer] Michael Pollan said, ‘Eat food, not too much, mostly plants,’ ” says Dr. Kara Parker, a family medicine and primary care practitioner at Hennepin Healthcare’s Whittier Clinic. “Processed foods are weight-promoting.”

Most processed foods contain unhealthy additives and “our metabolic machinery doesn’t really know what to do with them. Our metabolism can get slowed down by foods it doesn’t recognize,” she says. Shop the perimeter of the grocery store, where fresh produce, fresh meat and freshly frozen foods live.

Low-carb diets have been trendy in recent years — and, Parker says, many Americans could stand to eat fewer carbs. But carbs don’t need to be demonized — and we don’t necessarily need to go low carb, either. We may benefit simply by not overdoing them. “Keep carb and protein intake about equal,” she advises.

Her other essential advice? Always eat breakfast. The morning meal tells the body that you’re safe and fed; skipping it can trigger a starvation response, with the body clinging to calories. And opt for organic food as often as possible. Pesticide and herbicide residue on conventional foods can gunk up the metabolic machinery, just like the additives in most processed foods.

But don’t focus on food at the exclusion of other lifestyle factors. “We like to apply a one-dimensional solution to a four-dimensional problem,” says Dr. Thomas Sult, director of 3rd Opinion, a clinic in New London, Minn. Experts now understand that food is just one factor in the lifestyle habits that contribute to maintaining a healthy weight.

Exercise

One of those lifestyle factors, unsurprisingly, is exercise, and not just quantity. How you move can matter as much for weight loss as how much you move.

All movement is beneficial, and even small shifts, like taking the stairs instead of the escalator, can add up to better health.

But when weight loss is a primary goal, most people benefit by engaging in specific types of movement, including some bouts of vigorous exercise. “You can move, but if you don’t get your heart rate high enough once in a while, it won’t help you,” says Traci Mann, director of the Mann Lab at the University of Minnesota, where she researches eating behavior and body image. “And it’s possible to get 10,000 steps in a day without raising your heart rate.”

Mann is generally in step with the Centers for Disease Control and Prevention guidelines on exercise, which recommends 2½ hours a week of moderate-intensity exercise and 75 minutes a week of vigorous intensity aerobic activity, as a baseline for substantial health benefits.

Interval training is a great way to elevate your heart rate, Parker says. That means interspersing slow and steady movement with short bursts of intense exercise — or switch the two. Interval walking is a good example. Walk normally for a distance, then run as fast as you can for 10 seconds, then resume normal walking. Or speed walk most of your trek around the lake, cut up by short periods of walking at an average pace.

A note of caution: vigorous exercise is not for everyone (or it isn’t for everyone right away). Always consult a licensed health care provider before starting a new exercise routine.

Stress

Stress is inevitable, but the 24/7 stress some of us experience can directly affect weight. Says Sult: “Blood is shunted away from the gut and directed to the muscles” — the better to outrun a tiger on the savanna — “and that means you’re not digesting or absorbing your food well. Poor digestion and nutrient absorption is connected to weight loss resistance.

Unremitting stress can also trigger changes in the microbiome, or the collection of bugs that live in the gut, “and we now know that the health of the microbiome has a lot to do with gaining weight,” Sult says.

“We’re constantly in fight-or-flight, which leads to changes in the microbiome, poor digestion, and nutritional insufficiencies,” he says. When weight loss is a goal, prioritize stress management. Be deliberate and assertive about self care.

Sleep

A wealth of research now suggests that sleep deprivation and sleep disorders (such as sleep apnea) have a profoundly negative effect on metabolism. Getting too little sleep, getting too few consecutive hours of sleep, or not doing most of your sleeping when it’s dark outside (and most of your waking when it’s light outside) more or less ensures that stubborn weight won’t come off.

This is in part because ill-timed or insufficient sleep affects the genes that control metabolism. Feeling groggy the next day can also result in eating more carbs, Parker says. Waking up tired has most people reaching for dough­nuts and coffee, not boiled eggs and spinach. What’s more, adds Parker, “sleep apnea is so stressful on the body that it makes it very difficult to lose weight.” According to the American Sleep Apnea Association, some 22 million Americans have the condition — 80 percent of those cases undiagnosed.

Social, emotional and spiritual

Positive social interactions, a sense of purpose and a connection to something bigger than oneself all help balance the autonomic nervous system, says Sult — and that is a system we need working for us when weight is a problem.

“We live surrounded by people and still we feel lonely,” he says. Yet instead of carving out more time to see friends or finding what feeds us spiritually, we look for answers in the next pill or supplement. Or we try to eat our way to fulfillment.

• • •

If your eating is solid, your exercise is in sync and you’re paying attention to other important lifestyle factors but still not losing weight, consult a licensed health care provider, advises Parker. He or she can run tests and help identify underlying roadblocks to weight loss.

But don’t fall back into the old myth that making a single change or trying a new gimmick will help you achieve your goals. “When I was a young physician, I thought there must be a holy grail for weight loss,” says Sult. “But then I realized that weight loss isn’t about a diet or a supplement that can be bought on Amazon.”