4 Reasons Your Metabolism Slows When You Cut Calories

May 7, 2023

by Cathe Friedrich

Weight loss can be a complex and challenging journey. One of the most common tactics for shedding pounds is cutting calories. Adopting a low-calorie diet might seem like a surefire approach to losing weight, at least at first. But it’s not uncommon to hit a roadblock as your metabolism slows down in response to calorie restriction.

Here’s a frequent scenario. You cut back on calories, and the weight starts to come off. But then you hit a roadblock and your progress slows. You’re in good company! Many people experience a slowdown in their metabolism when they cut calories. The struggle is real, and it can make weight loss feel like an uphill battle.

Understanding why your metabolism slows when you cut calories will help you create a sustainable and successful weight loss plan. Let’s look at four reasons why this happens, and offer tips to help you overcome this challenge.

Basal Metabolic Rate (BMR) Slows

Basal Metabolic Rate (BMR) is the amount of energy your body needs to carry out basic metabolic functions, such as breathing, circulation, and maintaining organ function. This energy consumption accounts for approximately 60% to 70% of the calories you burn every day, and it varies from person to person.

Several factors influence BMR, including age, gender, weight, and body composition. Younger people tend to have a higher BMR, while older adults have a lower BMR, partially due to a loss of muscle mass related to aging. Muscle is more metabolically active than fat and burns more calories.

BMR can decline in response to weight loss and is a factor to consider when developing a weight loss plan. To continue losing weight, you may need to adjust your caloric intake and physical activity to compensate for the drop in BMR. Failure to do so could lead to a plateau or even weight gain. One way to counter this is to strength train.

Adding muscle mass through strength training will help boost BMR as the muscle you add requires more energy to maintain. Although strength training burns fewer calories per minute than aerobic exercise while you’re doing it, it can modestly increase the rate at which you burn energy.

Thermic Effect of Activity

The Thermic Effect of Activity (TEA) is another component of the total number of calories you expend each day. TEA represents the calories you burn through exercise and physical activity. As you lose weight and your body size diminishes you burn fewer calories both at rest and during physical activity. If you continue to eat the same number of calories, you’re no longer in a calorie deficit and you could see your weight loss decrease and even gain weight.

One of the most significant benefits of TEA is that it can help prevent the metabolic slowdown that often occurs as you lose weight. When you restrict your calorie intake, your body may try to conserve energy by reducing your metabolic rate, which makes it harder to lose weight. However, regular physical activity, including both cardio and strength training, helps maintain energy expenditure and prevent this slowdown. Additionally, TEA can help increase muscle mass, which is more metabolically active than fat tissue, meaning that it burns more calories at rest.

Thermic Effect of Food

The thermic effect of food (TEF) is a metabolic process where the body uses energy to digest, absorb, and metabolize the foods you eat. It’s a normal part of the body’s daily energy expenditure and typically accounts for about 10% of the calories you burn each day. However, during a caloric deficit, your TEF will drop, as you’re consuming less food. When you eat less, you expend fewer calories to digest and absorb it.

While TEF is not a significant contributor to the body’s overall energy expenditure, it is still a small factor that can impact the body’s metabolism. When in a caloric deficit, TEF can contribute to a slower metabolism, which is a normal response of the body to conserve energy.

Non-Exercise Activity Declines

NEAT, or non-exercise activity thermogenesis, has gained interest in recent years as a way to increase daily calorie expenditure. It’s the energy you expend during all activities of daily living that aren’t structured exercise. This includes everything from household chores to walking around the office to running errands.

While the exact number of calories burned during NEAT varies among individuals, it has been shown to make a significant impact on overall daily energy expenditure. Studies have found that some people can burn up to 2,000 more calories per day than others through NEAT alone. This means that even small changes in daily movements, such as taking the stairs instead of the elevator or standing while on a phone call, can add up to substantial calorie burn over time. Understanding and increasing NEAT can be a useful tool for weight management.

How to Prevent a Metabolic Slowdown

Once you know why your metabolism slows, you need to know how to prevent it. Here are some tips:

Eat enough protein: Consuming adequate protein can help maintain muscle mass, which can help keep your metabolism from slowing down.
Don’t skip meals: Skipping meals or going too long without eating can slow down your metabolism. Make sure to eat regular meals throughout the day.
Strength train: Building muscle through strength training can increase your metabolism, even when you’re not working out.
Stay hydrated: Drinking enough water can help keep your metabolism running smoothly.
Get enough sleep: Lack of sleep can disrupt your metabolism and cause it to slow down. Aim for 7-8 hours of sleep per night.
Consume enough calories: Severely restricting your calories can slow down your metabolism. Make sure you’re eating enough to support your body’s needs.
Incorporate high-intensity exercise: High-intensity exercise like sprinting or interval training can help boost your metabolism and burn more calories.
Eat enough fiber: Eating foods high in fiber can help keep you full and satisfied, which can prevent overeating and help maintain your metabolism.
Reduce stress: Chronic stress can slow down your metabolism. Incorporate stress-reducing practices like meditation or yoga into your routine.

Conclusion

Cutting calories alone may not be the best approach to losing weight. Your body has evolved to conserve energy, and when you cut calories, your metabolism slows as a way to protect against starvation. Instead, focus on a well-rounded approach to weight loss, including regular exercise, adequate sleep, and balanced nutrition. By taking a holistic approach, you can support your metabolism and achieve your weight loss goals in a healthy and sustainable way. Think of it as a marathon, not a sprint.

References:

“Components of Metabolic Rate – Doctor Steve Abel.” 03 Jan. 2023, https://www.doctorabel.us/human-nutrition/components-of-metabolic-rate.html.

Most J, Redman LM. Impact of calorie restriction on energy metabolism in humans. Exp Gerontol. 2020 May;133:110875. doi: 10.1016/j.exger.2020.110875. Epub 2020 Feb 11. PMID: 32057825; PMCID: PMC9036397.

“Metabolism and weight loss: How you burn calories – Mayo Clinic.” 08 Oct. 2022, https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508.

Dulloo AG, Jacquet J. Adaptive reduction in basal metabolic rate in response to food deprivation in humans: a role for feedback signals from fat stores. Am J Clin Nutr. 1998 Sep;68(3):599-606. doi: 10.1093/ajcn/68.3.599. PMID: 9734736.