Does Losing Weight Slow Your Metabolism?

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The Dead Golfer Capsule

If you’ve hit a weight loss plateau, you’re probably wondering, what gives? There are many reasons why weight loss might stall, but is your metabolism slowing down one of them?

Metabolism gets a lot of attention when it comes to weight loss. It also gets a lot of unnecessary credit and blame. Your metabolism matters when it comes to weight, but it’s not the only factor. Here, we explain the biological changes that occur in your metabolism and body during weight loss, and what you can do about it.

What is metabolism?

Metabolism refers to the necessary chemical processes that occur in the body in order to maintain life.

Think of your body as a car. If you put gasoline in your car, it uses this fuel to move. Likewise, your body uses calories, or energy, from food in order for it to move, breathe, and function. Metabolism is the process by which your body uses the energy you put in, or more simply, burns calories. You can also burn extra calories by increasing your activity, such as walking, dancing or exercising.

Your metabolism includes the following calorie-burning functions:

  • Basal or Resting Metabolic Rate (BMR or RMR):  BMR refers to how much energy (or calories) your body burns just to keep you alive. Even when you’re asleep, your body still uses energy to pump blood and keep your heart beating.
  • Thermic Effect of Food (TEF): Your body needs energy to process the food you eat. The thermic effect of food (TEF) includes the calories you burn when you digest food. So, yes, eating burns calories – although TEF is usually small enough not to exceed the calories you take in.
  • Non-Exercise Activity Thermogenesis (NEAT): NEAT refers to the calories your body burns through everyday activities, such as fidgeting, walking to work, or climbing stairs.

What is the Difference Between Fast Metabolism and Slow Metabolism?

A fast metabolism is one that burns a lot of calories to support its metabolism. Your friend can eat whatever they want without gaining weight, and they probably have a fast metabolism. In contrast, slow metabolism does not burn as many calories to support the same metabolic function.

You can blame genetics for this. “Many factors play a role in metabolism, including age, sex, genetics, body composition, and weight,” says Allison Knott, MS, RDN, a registered dietitian in Brooklyn, New York. While genetics largely determine how many calories you burn in various activities, you do have control over your metabolic rate.

Does Losing Weight Slow Your Metabolism?

Yes, it’s OK. If you eat fewer calories than you burn through your daily activities and exercise, you will lose weight. The hard part is keeping the weight off. Typically, someone loses weight, keeps it off for a while, and then recovers. Several factors are at play in this process, metabolism being just one of them.

You don’t need as many calories as 150 pounds to function at 200 pounds. Your BMR drops or slows down as you lose weight.

To add to the frustration, your brain also sends signals to your body that increase hunger and reduce the number of calories you burn. Evolutionarily speaking, this is a protective mechanism that prevents you from starving. Today, it is the leading cause of weight regain.

This may seem frustrating, but you do have control over how quickly your metabolism drops. You can prevent your metabolism from slowing down too much by losing weight slowly rather than by crash dieting.

“If you diet very aggressively, your metabolism goes down, which means you lose less weight than you lose calories. Slow dieting is less effective. Once you’ve lost weight and stabilized, if you’ve been eating every Monday Going up to a modest pace of two pounds doesn’t seem to have long-term effects. Your metabolism is lower because you are now a smaller person, but not disproportionately low.

Other Causes of a Slowed Metabolism

Weight loss isn’t the only culprit of a slowed metabolism. If you eat too few calories or go too long between meals (more than three or four hours), your metabolism will slow down. This is called “starvation mode” and is due to the same protective mechanisms that occur when you lose weight. Your body slows down the rate at which it burns calories in order to conserve energy because it doesn’t know when you’re going to feed it again. If you’re severely restricting calories to lose weight, it’s a double whammy.

The ratio of body fat to muscle also affects metabolic rate. Body weight or body composition is made up of fat, muscle, bone and water. Muscle is more metabolically active than fat. In other words, it burns more calories. When you lose weight, you lose fat and muscle unless you are doing something to maintain muscle mass. Losing lean muscle mass that burns calories slows down your metabolism.

“That’s one of the reasons why you see changes in metabolism over a lifetime,” Knott said. “As you age, you naturally lose muscle mass, which leads to a decline in metabolism. This can be influenced by maintaining muscle mass through weight-bearing physical activity throughout the lifespan.

Is Your Metabolism Below “Normal” Levels From Weight Loss?

There is no “normal” metabolism. What is normal for you is based on your genes, age, gender, weight and activity level. But things that you think are normal can change over time due to age, weight loss or muscle loss.

“Some newer studies have shown that significant weight loss can lead to a lower than ‘normal’ metabolic rate for that body weight, which remains lower even after weight regain,” Anzlovar said. “This means that if you started at 200 pounds and now weigh 150 pounds, you’re going to burn fewer calories both at rest and during exercise than someone who always weighed 150 pounds. It’s even more exciting for people trying to lose weight.” Frustratingly, studies also show that if someone who loses 50 pounds regains weight, his or her metabolism will be below 200. She adds that it’s not clear if this always happens, or why.

Can you boost your metabolism?

You may feel like your metabolism is doomed, but there are a few things you can do to keep your metabolism revved up and keep it from slowing down.

  • Eat plenty of high-quality foods. Stick to whole, unprocessed foods, and eat them often. “Eating a very low-calorie diet or exercising excessively while not eating enough can often lead to a slower metabolism,” Anzlovar said. Her clients are often surprised when she tells them they need to eat more. Eat every three to four hours to prevent starvation mode telling your body to conserve energy instead of burning it.
  • Focus on protein and fiber. According to Roberts, research into lower-than-normal metabolism is ongoing. “Maybe a high-protein diet helps prevent falls,” she said. “Furthermore, a high-fiber diet would definitely have a protective effect. She and her colleagues found that when people at a stable weight substituted whole grains for refined grains, they were able to modestly increase their BMR (or RMR). That’s why a high-fiber diet is the cornerstone of her weight loss plan. Other studies have confirmed that eating foods that are high in protein and fiber and low on the glycemic index leads to less hunger and a higher feeling of fullness, which helps counteract the increased hunger associated with weight loss. Aim for at least 25 to 35 grams of fiber per day.
  • Pick up the weights. “Physical activity is one of the few ways in which metabolism is significantly affected, both because of the extra energy required to be active and because of changes in body composition,” Knott said. Don’t just focus on cardio, add weight-bearing activities as well. Cardio may give you a higher total calorie burn, but it means you lose fat and muscle. Add strength training two to three days per week to help lose fat while preserving muscle. “More muscle mass means a higher metabolism, so don’t be afraid of weight training,” says Anzlovar.
  • get moving. Studies have shown that people who are able to keep their weight off exercise for nearly an hour a day on a long-term basis. The National Weight Control Registry, a database that tracks people who have successfully lost weight and kept it off, reports that 90 percent of its members exercise an average of one hour a day. Studies have also shown that people who burn a lot of calories through daily exercise but eat enough to maintain their weight can increase their metabolic rate. Roberts adds: “Exercise has a short-lived effect. For a while after exercising, your metabolism increases. Then, the gain in muscle mass you gain from weights will make a small difference in the long run.

Unfortunately, losing weight will slow down your metabolism, but you do have some control. Ban crash diets and work on changing habits. When you lose weight, you burn fewer calories and may be hungrier, but you can offset that by eating foods high in protein and fiber, substituting whole grains for refined grains, and doing daily cardio and strength training.

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