Earlier studies measuring glucose uptake in the brain during childhood suggest some of this work is neuronal growth and synapse development.

Maturation in other systems no doubt contributes as well. Metabolism stays elevated through childhood, slowly decelerating through adolescence to land at adult levels around age Boys decline more slowly than girls, consistent with boys' slower development, but there's no bump at puberty in males or females.

Perhaps the biggest surprise was the stability of our metabolism through middle age. Daily energy expenditures hold remarkably steady from age 20 to No middle age slowdown, no change with menopause.

The weight gain so many of us experience in adulthood cannot be blamed on a declining metabolism. As a man in my 40s, I had sort of believed the folk wisdom that metabolism slowed as we aged.

My body definitely feels different than it did 10 or 20 years ago. But like hunting some metabolic Sasquatch, when you actually look there's nothing there. Same for the much touted metabolic differences between men and women.

Women have lower daily energy expenditures on average, but that is only because women tend to be smaller and carry more of their weight as fat.

Compare men and women with the same body weight and body fat percentage, and the metabolic difference disappears. We did find a decline in metabolism with age, but it doesn't kick in until we hit After 60, metabolism slows by around 7 percent per decade.

By the time men and women are in their 90s, their daily expenditures are 20 to 25 percent lower, on average, than those of adults in their 50s. That's after we account for body size and composition. Weight loss with old age, especially diminished muscle mass, compounds the decline in expenditure.

As with all age groups, there's a good amount of individual variability. Maintaining a younger, faster metabolism into old age might be a sign of aging well, or perhaps it is even protective against heart disease, dementia and other age-related disease.

We can now start to investigate these connections. Guided by our metabolic road map, we have a new world of research ahead of us.

What is already apparent, however, is that a bite of birthday cake does different things for a seven-year-old girl, her middle-aged dad and her elderly grandmother.

Clara's bite is likely to be gobbled up by busy cells, fueling development. Mine might go to maintenance, repairing all the little bits of damage accrued through the course of the day. As for Grandma, her aging cells might be slow to use the calories at all, storing them instead as glycogen or fat.

Indeed, for any of us, the cake will end up as fat if we eat more calories than we burn. The road map also highlights a major conundrum of the human condition. Whether they're born into a hunter-gatherer camp, a farming village or an industrial megacity, human youngsters need a lot of help getting food.

Other apes learn to forage for themselves by the time they stop nursing, around the age of three or four. Our children are wholly dependent on others for food for years and aren't self-sufficient until their teens. And those least able to fend for themselves have the greatest energy needs.

Not only has our species evolved a faster metabolic rate and greater energy demands than other apes, but we must also provision each costly offspring for more than a decade.

Where do we get all those calories? Recently my colleagues and I worked out this part of the human energy equation, too. The question of calories looms largest in hunter-gatherer and farming communities, where daily life revolves around food production.

For most of our species' history, as for most species, there was no other line of work. Every kid knew what they were going to be when they grew up. As late as the mids, more than half of the American workforce was made up of farmers.

For the past decade I've been working with colleagues to understand the calorie economy in the Hadza community of northern Tanzania. The Hadza are a small population of 1, or so, and about half of them maintain a traditional hunting-and-gathering way of life, foraging on the savanna landscape they call home.

No population alive today is a perfect model of the past, but groups like the Hadza, who continue these traditions, provide a living example of how these systems work. Men spend most days hunting with bow and arrow or chopping into hollow tree limbs to pillage honey from beehives. Women gather berries and other plant foods or dig for wild tubers in the rocky soil.

Hadza camps, small collections of grass houses tucked among the acacia trees, are alive all day with kids being kids, running around, laughing, playing—and waiting for adults to bring them food. We've measured Hadza energy budgets using doubly labeled water, giving us a clear idea of the calories men and women consume and expend each day.

We've also lugged portable respirometry equipment into the bush, a metabolic lab in a briefcase, to measure the energy costs of foraging activities such as walking, climbing, digging tubers and chopping trees.

And we've got years of careful observation recording the hours spent each day on different foraging tasks and the amount of food acquired. After more than a decade of work, we've got a complete accounting of the Hadza energy economy: the calories spent to get food, the calories acquired, the proportions shared and consumed.

Tom Kraft of the University of Utah led our team's effort to compare the energy budgets of the Hadza population with similar data from other human groups and from other species of apes.

It was a massive project, with researchers poring over old ethnographic accounts of hunter-gatherer and farming groups and combing through ecological studies and doubly labeled water measurements in apes to reconstruct their foraging economies.

But when we were finished, what emerged was a new understanding of the energetic foundation for our species' success. We could finally see where all those calories come from, the energy needed to fuel expensive human metabolisms and provision helpless kids.

It turns out humans' unique, cooperative foraging strategy, combined with our clever brains and tools, makes hunting and gathering extremely productive.

Even in the harsh, dry savanna of northern Tanzania, Hadza men and women acquire to 1, kilocalories of food an hour, on average. Ethnographic records from other groups around the world suggest these rates are typical for hunter-gatherers.

Five hours of hunting and gathering can reliably bring in 3, to 5, kilocalories of food, enough to meet a forager's daily needs and provision the camps' children. It's the positive feedback engine that propelled the human species to new heights.

Hunting and gathering is so productive that it creates an energy surplus. Those extra calories are channeled to offspring, meaning they can take longer to develop, learning skills that make them effective foragers.

Reaching adulthood, they'll do just as their parents did, acquiring extra food and plowing those calories into the next generation. Over evolutionary time childhood grows longer as foraging strategies grow more complex. Life spans get extended, too, with natural selection favoring additional years of productive foraging to support children and grandchildren.

Grandparents, once rare, become a fixture of the social network. Apes in the wild are not nearly as productive in gathering food. A forensic accounting of the energy budgets for chimpanzees, gorillas and orangutans shows that males and females get around to kilocalories an hour.

It takes them seven hours of foraging just to meet their own needs each day. No wonder they don't share. Our hyperproductive foraging isn't cheap. People in hunter-gatherer communities expend more than twice as much energy to acquire food as apes in the wild.

Surprisingly, human technology and smarts don't make us very energy-efficient. Hadza men and women achieve the same paltry ratio of energy acquired to energy expended that we find in wild apes.

Cooperation and culture enable human foragers to be incredibly time-efficient, acquiring lots of calories an hour, but our unique foraging strategies are still energetically demanding. Hunting and gathering is hard work.

Farming isn't any easier, but our analyses found it can be even more productive. When we compared the energy budgets for the Hadza and other hunter-gatherer populations with those of traditional farming groups, we found that farmers typically produce far more calories an hour.

The Tsimane community, a population in the Amazonian rain forest of Bolivia, provides a useful point of comparison. The Tsimane get most of their calories from farming, but they also hunt, fish and collect wild plants. With farmed foods as their energy staple, they produce nearly twice as many calories an hour as the Hadza.

They're more energy-efficient as well, getting more food from every calorie they spend foraging and farming. Those extra calories are embodied in the children running around Tsimane villages. More food and faster production mean a lighter workload for mothers because others in the community can more easily share the time and energy costs of caring for kids.

As with many subsistence farming communities, Tsimane families tend to be large. Women have an average of nine children over the course of their lives. Compare that with the average fertility rate of six children per mother in the Hadza community, and the impact of that extra energy is inescapable.

And it's not just the Tsimane. Farming communities tend to have higher fertility rates than hunter-gatherer communities. Increased fertility is an important reason farming overtook hunting and gathering in the Neolithic age, the time spanning roughly 12, to 6, years ago.

Archaeological sites across Eurasia and the Americas document a rising tide of children and adolescents following the development of agriculture. From this perspective, a kid's birthday party is more than a personal milestone. It's a celebration of our improbable evolutionary story.

There's the food, of course. We get the flour and sugar for the cake from our farming ancestors, the fire to bake it from the Paleolithic era.

The milk and eggs come from animals that we've completely transformed from species we once hunted, shaped to our will over generations of careful husbandry. And there's the calendar we use to mark our days and measure our years, an invention of agriculturalists who needed to know precisely when to reap and sow.

Hunter-gatherers track the seasons and lunar cycles but have little use for accurate annual calendars. There are no birthdays in a Hadza camp. But the key element of any celebration is the community of friends and relatives, multiple generations gathering to eat and laugh and sing.

Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map. Eur J Clin Nutr. Pethusamy K, Gupta A, Yadav R. Basal metabolic rate Bmr. In: Vonk J, Shackelford T, eds. Encyclopedia of Animal Cognition and Behavior. Springer International Publishing; Ravn AM, Gregersen NT, Christensen R, et al.

Thermic effect of a meal and appetite in adults: An individual participant data meta-analysis of meal-test trials. Food Nutr Res. Published Dec By Malia Frey, M. Use limited data to select advertising. Create profiles for personalised advertising. Use profiles to select personalised advertising.

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Table of Contents. What Is Resting Metabolic Rate? How to Calculate Your BMR. How to Use BMR to Lose Weight. What is Basal Metabolic Rate? Equation to Calculate Your BMR The Harris-Benedict Equation is often used to estimate basal metabolic rate. How to Change Your Body Composition. How to Boost Your Daily Energy Expenditure.

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In fact, about 60 to 75 percent of your TEE consists of this type of passive calorie burn, known as resting metabolic rate RMR. Many factors influence whether someone has a high or low resting metabolic rate, and thus burns more or less calories during the day without even trying.

These include:. Although there are things you can do to increase or decrease your RMR, some people may be genetically predisposed to faster or slower metabolism.

Lean Body Mass Lean. Muscle tissue requires more oxygen than fat tissue does, which means your body has to spend more energy to maintain it. Total Body Weight and Size. A larger, heavier body burns more calories at rest than a small one. So as you lose weight, your RMR will decrease. As you get older, your RMR slows down and your body burns fewer calories at rest.

This is due to fluctuating hormone levels, and, for most people, decreased muscle mass and less physical activity. Calorie Intake Eating. significantly fewer calories than your body needs, like in the case of an extreme diet, can send your body into survival mode in which calories are conserved rather than burned, lowering your RMR.

Meal Frequency. About five to 10 percent of the calories you eat are used to fuel the digestion process. External Factors.

Lifestyle and environmental factors that can affect RMR include extreme hot or cold temperatures, certain medications, herbs and supplements, smoking, stress, the health of your immune system and the amount of sleep you get. These basic calculations cannot take into account all of the factors that affect your metabolism, but it is still possible to estimate your metabolic rate based on your body weight and fitness level.

Some simple math may open your eyes to new ways of thinking about your weight loss or maintenance strategies. To estimate your RMR, multiply your body weight in pounds by Tip: Grill, stuff, steam, bake or stir-fry a serving of peppers, or serve them raw to pair with low-fat dips or cottage cheese.

Metabolism-Boosting Powers: Chicken, turkey and other protein-packed lean meats take more energy for your body to break down than carbohydrate or fat-rich foods, therefore, burning slightly more calories during the digestive process.

Tip: Trim off any visible fat from meat and poultry, including the skin. Low-fat cooking methods include broiling, roasting, sautéing, grilling and baking. Metabolism-Boosting Powers: The calcium and vitamin D found in milk are essential for building dense muscle mass, which is important for overall health.

Tip: Add low-fat milk instead of water to oatmeal, hot cereals and condensed cream soup. Metabolism-Boosting Powers: Broccoli is a member of the cruciferous vegetable family. It's known for its high water and fiber content, which is a great combination to help you feel full.

Tip: Eat broccoli steamed or roasted. Or, enjoy it raw with a low-fat veggie dip. Metabolism-Boosting Powers: Lentils are a type of legume and are packed with iron, magnesium and potassium. They are a great plant protein and fiber source with 8 grams of each.

Lentils come in a variety of colors including red, brown, green and yellow. All are equally healthy for you. Tip: Adult women should get more than twice the amount of iron as men. One cup of lentils provides about 35 percent of your daily iron needs.

Metabolism-Boosting Powers: This is a powerhouse full of fiber that will not only help you last through the morning without hunger but will slow down the release of sugar into your blood stream. Tip: Start the day with a hot bowl of oatmeal in the morning or make overnight oats the night before in a mason jar for an on-the-go breakfast.

Metabolism-Boosting Powers: Berries, such as blueberries and strawberries, are low in calories and high in fiber. Fiber promotes overall weight loss by reducing your appetite. Metabolism-Boosting Powers: Almonds contain lots of healthy fats, fiber and protein, which is a combination that curbs hunger.

Tip: Enjoy a handful of almonds between meals to avoid unhealthy snacks or chop them up for a crunchy salad topper. Metabolism-Boosting Powers: Cottage cheese is low in fat, low in carbs and high in protein, making it ideal for healthy eaters.

Tip: Add a scoop of low-fat cottage cheese to a berry smoothie for a non-traditional twist. Metabolism-Boosting Powers: Tempeh is a great protein substitute for meat if you are looking for a vegetarian option.

Metabolism-Boosting Powers: Water can suppress your appetite and maybe boost your metabolism for a short amount of time. Research suggests the more hydrated you are , the better able your body is at just about everything from thinking to making exercise easier. Tip: Try starting the day off with a glass of water or drink a glass before you eat your meals.

To determine how much water to drink per day, divide your weight in half. The number you get should be your liquid amount in ounces. Besides these healthy eating tips, one of the best ways to speed up your metabolism is with weight or muscle strengthening.

Lean muscle mass increases your metabolism. Muscle is metabolically active, which means people with lean, muscular bodies need more energy to function than people with a higher percentage of body fat.

Make sure to talk with your doctor before beginning any new workout routine.