We all know those irritating people who seem to eat endlessly and still stay thin. “They have a fast metabolism,” we tell ourselves. But metabolism is about far more than how many calories go in, or which genetic tendency we inherited.
Metabolism is also shaped by everyday habits repeated over time, including how much we move, how well we sleep, the quality of our food and the amount of muscle mass we manage to preserve. Before trying to “speed up” metabolism, it may be more useful to identify the habits that can quietly harm it.
Here are five of them.
Sitting for hours without getting up
One of the most modern, and most damaging, habits for metabolic health is prolonged sitting.
“We are creatures meant to be active, but our lifestyle has made us very sedentary,” says Dr. Liat Barzilai-Yosef, a specialist in internal medicine and endocrinology and director of the obesity treatment clinic at Meir Medical Center. “In the past, people were more active throughout the day. Today, for many of us, work means sitting in front of a computer and a screen.”
The problem is not only that we burn fewer calories.
“Some of the metabolic diseases we see today are connected not only to less healthy, more processed diets, but also to the fact that the body works less,” Barzilai-Yosef explains. “In the past, most people went out to work and the body worked. Today, in many cases, mainly the brain works.”
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Prolonged sitting reduces stimulation to different tissues in the body, especially muscles, but also fat tissue. When the body barely moves for hours, metabolic activity changes as well. Over time, sedentary behavior is associated with a higher risk of insulin resistance, obesity, diabetes, high blood pressure, cardiovascular disease and atherosclerosis.
Research supports this connection. A meta-analysis of trials that interrupted prolonged sitting with short activity breaks found that movement breaks modestly reduced post-meal rises in glucose, insulin and triglycerides compared with uninterrupted sitting. In practical terms, even short, light movement during the day can affect how the body handles sugar and fats in the blood.
The goal, Barzilai-Yosef says, is not necessarily to turn every workday into a workout. It is simply to break up long stretches of sitting.
“You need to interrupt every hour of sitting with movement, even light movement,” she says. “Get up for two minutes, stretch, take the stairs, walk to fill a glass of water or simply move around a little. The fact that the body moves after an hour of sitting helps restore stimulation to the muscles and tissues, improve insulin sensitivity and reduce insulin resistance.”
Sedentary living, one of the defining problems of 21st-century life
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Smartwatches and apps that remind users to stand up are based on the same principle, she adds. “Their goal is to wake up someone who has been sitting for a long time and get them moving again. This is something that needs to be part of our awareness.”
Barzilai-Yosef tries to apply the principle in her own workday. “As a doctor who treats diabetes and obesity, I work a lot in an office. I chose a work pattern in which I get up for every patient: I get up for a physical exam, get up to measure, get up to walk the patient to the door and then get up again to call in the next patient. If I see 18 patients a day, I have stood up at least 18 times, and often more.”
Everyone, she says, can find a version that fits their day. “Even a CEO with an assistant can decide that some things will not be done by phone or email, but by getting up and walking a few steps. If you need water or a drink, you do not have to ask someone to bring it. You can get up and take it yourself. The idea is not to add another burdensome task to the workday, but to integrate movement naturally into the routine.”
הפסקת יזומות לשבירת רצף הישיבה יעזרו להפחית הסיכון למחלות מטבוליות
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Skipping strength training
For years, when people spoke about exercise and health, the emphasis was mostly on aerobic activity such as walking, running, swimming or cycling. All of those are important. But when it comes to metabolism, there is another component many still overlook: strength training.
“There was a long period when people mainly talked about aerobic exercise,” Barzilai-Yosef says. “Fortunately, that is beginning to change. Today there is almost no medical conference where people are not talking about sarcopenia, or loss of muscle mass. We now understand that muscle tissue is not only a matter of strength or appearance, but a highly significant tissue in terms of metabolism.”
Aerobic exercise matters, but strength training matters just as much
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Beginning around age 40, she says, people already experience some natural decline in muscle mass. “In women, this process can intensify around menopause because of the decline in estrogen. In men, the hormonal decline is usually more gradual, but it also has an effect. These changes alter body composition: less muscle tissue and more fat tissue.”
That is where strength training comes in.
Aerobic exercise improves heart and lung endurance, helps maintain weight and contributes to reducing insulin resistance. But it is not always enough to build or preserve muscle.
“Aerobic training is wonderful and has many benefits,” Barzilai-Yosef says. “But it does not activate all muscle groups sufficiently, and it does not always create the stimulus needed to build or preserve muscle mass.”
The importance of muscle is not limited to how many calories the body burns at rest. Muscle tissue is one of the main tissues that absorb glucose from the blood, giving it an important role in insulin sensitivity and blood sugar balance.
“When there is more active muscle tissue, the body has a better ability to absorb glucose into the muscle,” she explains. “That helps improve insulin sensitivity and reduce insulin resistance. That is why we want more muscle tissue and less visceral, or abdominal, fat, which is linked to more inflammation and more insulin resistance.”
Research also supports making strength training part of a healthy routine. A 2020 review in Frontiers in Physiology noted that skeletal muscle is one of the body’s central organs for blood sugar regulation and is responsible for about 80% of glucose uptake from the blood after a meal. Another meta-analysis, published in 2022 in Obesity Reviews and including randomized studies of people with overweight or obesity, found that resistance training helped reduce fat mass and preserve or increase lean body mass, especially when combined with dietary change.
In other words, the value of strength training is not only weight loss, but improved body composition.
“The basic recommendation is to do strength training at least twice a week, working the large muscle groups,” Barzilai-Yosef says. “The goal is not for every person to become an athlete, but to understand that muscle is an inseparable part of metabolic health.”
Sleeping too little, or at irregular hours
Sleep is sometimes treated as something that can be trimmed when there is not enough time. Many people recognize the pattern: one more hour of television, one more hour of work, one more late-night scroll. But from a metabolic standpoint, the body sees sleep very differently.
“Sleep is the body’s charging point,” Barzilai-Yosef says. “During sleep, the body goes through a process of relaxation and recovery, not only cognitive and mental, but also physical and metabolic.”
Many of the hormonal processes related to metabolism, insulin sensitivity and hunger and satiety are affected by sleep quality and duration.
Sleep is the body’s charging point. No wonder it affects metabolism too
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“We know that people who do not sleep enough are affected not only in concentration and daily functioning,” she says. “With sleep deprivation, insulin resistance also rises, the sympathetic nervous system becomes more active and there is an effect on hormones related to hunger and satiety.”
The impact is also felt in daily behavior. When we are tired, the body looks for ways to keep itself awake: more coffee, more energy drinks, more easily available carbohydrates and more snacking.
“Tired people tend to eat more during the day, and especially to choose calorie-dense foods,” Barzilai-Yosef says. “They are looking for something that will wake them up, that will help them stay alert. Over time, this can contribute to weight gain and harm metabolic health.”
According to the CDC, regularly sleeping less than seven hours has been associated with a higher risk of obesity, diabetes, high blood pressure, heart disease and stroke.
Here, too, the research supports the link, though precision matters. Short sleep does not necessarily slow metabolism directly, but it does affect the way the body handles energy, hunger and sugar. A meta-analysis published in 2019 in Sleep Medicine Reviews found that sleep restriction reduced insulin sensitivity and affected brain regions related to reward and self-control around food. Another meta-analysis, published in the European Journal of Clinical Nutrition, found that partial sleep deprivation increased daily energy intake without a clear parallel change in energy expenditure.
That is why sleep should be treated with the same seriousness as nutrition and physical activity, Barzilai-Yosef says.
“We need to treat sleep as one of the body’s most important chargers, not as something we can skip,” she says. “The recommendation for adults is generally to sleep at least seven hours a night.”
The solution begins with awareness and consistent habits: going to sleep and waking up at similar times, reducing screens and social-media scrolling before bed, not turning the bed into an extension of the workday and using the evening window when the body begins secreting melatonin and preparing for sleep.
“We live in a world that operates 24/7, and screens and social networks are very addictive,” she says. “But someone who has difficulty sleeping over time should not simply accept it. There are sleep clinics, sleep labs and medication, cognitive and behavioral treatments that can help. The main thing is not to dismiss sleep.”
Eating too little protein and fiber during the day
It is not only excess of certain foods that can harm metabolic health. Sometimes the problem is what is missing from the plate.
A diet low in protein and fiber can impair satiety, make it harder to maintain muscle mass and affect the way the body handles sugar and energy throughout the day.
Foods rich in dietary fiber
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“Fiber is not only something that helps digestion,” says Dr. Deeb Daoud, an endocrinologist at Assuta Medical Centers. “It affects the balance of bacteria in the gut, and those bacteria are significant partners in managing weight and the body’s energy balance.”
The connection is also supported in the scientific literature. Dietary fiber, especially fiber fermented by gut bacteria, is linked to the production of short-chain fatty acids and to improvement in measures related to insulin sensitivity, blood sugar regulation and inflammation. A review published in the American Journal of Lifestyle Medicine emphasized that higher fiber intake is associated with better metabolic health, including through effects on the microbiome, blood sugar and satiety.
Protein also plays an important role because of its effect on muscle mass.
“When people greatly reduce the amount of protein in their diet, they may harm their feeling of satiety and their ability to maintain muscle mass,” Daoud says.
But precision is important: Protein does not “cancel” insulin secretion, and sometimes it also stimulates insulin secretion. Compared with a meal based mainly on fast-available carbohydrates and low in fiber, however, a meal containing protein, vegetables and fiber tends to be more filling and to produce a more moderate glycemic response.
That is why, Daoud says, one simple recommendation is not only what to eat, but in what order.
“It is better to start the meal with protein and fiber, and only afterward get to the carbohydrates,” he says. “That way we moderate the body’s response to the meal.”
Research on meal sequencing has found that eating vegetables or protein before carbohydrates can reduce the rise in glucose and insulin after a meal, especially among people with diabetes or prediabetes.
“The practical recommendation is to aim for sufficient fiber intake, generally around at least 25 grams a day, and in some guidelines 22 to 34 grams a day depending on age and sex, and protein intake suited to body weight, age, activity level and health status,” Daoud says.
For many adults, he says, that means at least 1 to 1.2 grams of protein per kilogram of body weight per day, especially when there is concern about loss of muscle mass, though it should be adjusted individually.
“This is not only a question of diet,” he says. “The goal is to build meals that create satiety, preserve muscle and reduce sharp fluctuations in sugar and insulin throughout the day.”
Eating too much ultra-processed food
One thing that can harm metabolism is not only what we eat, but also the form in which food reaches us.
Ultra-processed foods, including snacks, industrial baked goods, sweetened breakfast cereals, sugary drinks, ready-made meals and packaged products with long ingredient lists, are often designed to be available, highly palatable and quick to eat. That combination can lead us to consume more energy than the body needs before satiety mechanisms have time to respond.
Ultra-processed food makes weight regulation harder
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“The problem with ultra-processed food is not only the calories,” Daoud says. “These are foods that usually contain many readily available carbohydrates, little fiber and sometimes a lower-quality fat composition. After such a meal, blood sugar can rise more quickly, and so can the insulin response.”
Insulin is an important hormone, he adds, but when the body is repeatedly required to produce sharp responses like this, it can make weight regulation and metabolic health more difficult.
The issue was examined in a controlled intervention study published in 2019 in Cell Metabolism. In the study, conducted at the NIH Clinical Center, 20 participants received an ultra-processed diet for two weeks and an unprocessed diet for another two weeks, in random order. The menus were matched for the calories presented to participants, as well as carbohydrates, fat, protein, sugar, sodium and fiber, but participants could eat as much as they wanted.
During the period in which they ate the ultra-processed diet, they consumed an average of about 500 more calories per day and gained weight. During the unprocessed diet period, they lost weight.
“The recommendation is not to panic over every packaged product, but to try to base most of the diet on food that is as minimally processed as possible,” Daoud says. “The simpler the food, the richer it is in protein and fiber, and the more it requires the body to chew and digest, the easier it is to maintain satiety, a more moderate response to meals and more balanced metabolism.”