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Does the Time of Day Affect How Many Calories You Burn?

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Today, there are many resources available for those interested in burning calories. There are trackers and apps to calculate how many steps you’ve taken; how many calories you’ve consumed; and how much water you drank. The tools provided to track calories consumed and burned, reduce the task to a simple game of addition and subtraction. However, after a pattern is developed, people often want to figure out how to maximize the results of their efforts. After all, the hard work of exercise, eating, sleeping and staying hydrated properly is difficult. Wanting it to pay off as much as possible is natural.

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Scientific studies have risen to the occasion by conducting research on correlations between circadian rhythms and amount of calories burned. This allows people to make choices: when should they work out to maximize calories burned? How are calories burned in the first place? Does sleeping burn calories?

How Do You Burn Calories?

Learning about weight loss and how to best burn calories is a hot topic in the United States. This is because 66 percent of adults are obese or overweight.1 However, on a biological level, burning calories is simple math. Each person burns a different number of calories to conduct basic functions: breathing, digesting food, pumping blood and maintaining homeostasis. This number of calories burned increases when other activities are added: physical labor, exercise, or walking from point A to point B.

Calories are stored in an imaginary bank, and any sort of activity (even homeostasis) subtracts from the number in that bank. Excess calories that remain unused are stored in the body for future use when the body’s needs exceed the amount of calories available.

How Many Calories Do You Burn While You’re Asleep?

Not getting enough sleep puts more stress on your body.

According to medical studies “women who reported sleeping 5 or fewer hours per night were at greater risk for weight gain and in general weighed more compared with women who slept 7–8 hours per night.”2

Additionally, calories are indeed burned during sleep. The actual number varies based on multiple individual factors. Most estimates change based on body weight, but a solid estimate is 300-400 calories burned over the course of a good night’s sleep.2

Is Working Out in the Morning Better for Weight Loss?

Studies show that different types of exercise tend to affect the body differently, at different times of day. Common exercise categories include aerobic training, and resistance training.

Aerobic training is associated with most common forms of cardio: running, dancing, swimming, kickboxing, and cardio machines. This is a focus for people who want to lose weight. The deficit produced by calories consumed, minus calories burned, equals weight loss.

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On the contrary, resistance training can take many forms, but is often associated with hitting the gym and lifting weights. This can sometimes add pounds to your overall body weight, but in the form of muscle. It can also be thought of as strength training. Due to the different biological requirements of these types of training, researchers discovered a difference in people that exercise in the morning.

Do You Burn More Calories in the Morning or Evening?

Research shows that more calories are burned with morning exercise. This is because actively burning calories usually requires some form of aerobic exercise. While actively expending calories is an obvious benefit of aerobic exercise, it also improves blood flow and oxygen consumption.

The researchers observed that the endurance exercise capacity of men during exhaustive cycling exercise at 65 percent peak VO2 was significantly greater in the morning than in the evening. In addition … a two-month aerobic exercise program, which consisted of ergometer cycling, increased the heart rate in the morning.3

Does It Matter What Time of Day You Exercise to Lose Weight?

According to studies conducted by Appalachian State University, the time of day that you exercise has a pronounced effect on weight loss. This is largely due to the body’s tendency to self-regulate by lowering it’s own blood pressure in the evening hours. If your blood pressure is too high at night, it may contribute to insomnia and other sleep troubles. Lowering your blood pressure is the body’s way of preparing itself for a refreshing night’s sleep.

Conversely, the body is waking up and preparing to engage in physical and biological labor for the day. Blood pressure tends to be higher in the morning, then. In this study, exercise conducted in the afternoon showed no pros or cons either way.

SEX OR CARDIO: Which Burns More Calories?

Within this study, the researchers used middle-aged study participants, who walked on the treadmill. They were divided into three groups, and each exercised at a different time of day. Some exercised in the early morning, others in the early afternoon, and the rest in the evening.

In all cases, those who exercised at 7 a.m. experienced about a 10 percent reduction in blood pressure that carried through the remainder of the day. They also had about a 25 percent dip in blood pressure at night, slept longer and had more beneficial sleep cycles than when they exercised at other times of the day.4

How Many Calories Do You Burn in a Day?

The number of calories burned in a day depends on multiple factors. Using the Harrison-Benedict formula helps to get a fairly accurate idea. This formula is different for men and women. It starts at a base point: given your gender, age, weight, and daily activities, how many calories would you need to consume in order to maintain your current weight?

The formula for men is: 66 + (6.2 x weight) + (12.7 x height) – (6.76 x age)=BMR. The formula for women is: 655.1 + (4.35 x weight) + (4.7 x height) – (4.7 x age) = BMR for women.5

To calculate the formula for a 29-year-old man who is six feet tall and weighs 200 pounds, this equals a BMR of approximately 2,024. This is multiplied by an activity number, which ranges from 1.2-1.9.

  • 1.2: sedentary (little to no exercise)
  • 1.375: lightly active (light exercise 1-3 days per week)
  • 1.55: moderately active (moderate exercise 3-5 days per week)
  • 1.725: very active (hard exercise 6-7 days per week)
  • 1.9: extra active (very hard exercise/training or physical job)6

When the BMR is multiplied by this number, it produces the amount of calories necessary to maintain current weight. This number can be adjusted in order to create a calorie deficit, which usually equals weight loss. The total number of calories burned must be subtracted from the number of calories consumed at meals.

How to Maximize Calories Burned

Another way to burn the most calories is to take advantage of the morning workout. If you engage in intense exercise on an empty stomach, you may burn more fat. This is because “fasting before exercise increases fat utilization.”7

Fasting before exercise increases fat utilization.

It is the same principle at work when your body temperatures are low. The body will burn fat stores in order to warm itself. In the same vein, the body will take advantage of your fasted state, when you engage in morning workouts before eating. When your body realizes it’s time to work and engage in physical activity, you will benefit with more energy and more calories burned.

Citations and Sources

1.
Swift D, Johannsen N, Lavie C, Earnest C, Church T. The Role of Exercise and Physical Activity in Weight Loss and Maintenance. Prog Cardiovasc Dis. 2013;56(4):441-447. [PMC]
2.
Spivey A. Lose Sleep, Gain Weight: Another Piece of the Obesity Puzzle. Environ Health Perspect. 2010;118(1):A28-A33. [PMC]
3.
Seo D, Lee S, Kim N, et al. Morning and evening exercise. Integr Med Res. 2013;2(4):139-144. [PMC]
4.
Early morning exercise is best for reducing blood pressure and improving sleep. Appalachian State University. http://newsarchive.appstate.edu/2011/06/13/early-morning-exercise/. Published June 13, 2011. Accessed January 15, 2019.
5.
Douglas C, Lawrence J, Bush N, Oster R, Gower B, Darnell B. Ability of the Harris Benedict formula to predict energy requirements differs with weight history and ethnicity. Nutr Res. 2007;27(4):194-199. [PMC]
6.
How Many Calories Do I Burn in a Day? Healthline. https://www.healthline.com/health/fitness-exercise/how-many-calories-do-i-burn-a-day#calories-burned. Published 2017. Accessed January 15, 2019.
7.
Dohm G, Beeker R, Israel R, Tapscott E. Metabolic responses to exercise after fasting. J Appl Physiol (1985). 1986;61(4):1363-1368. [PubMed]
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Cassandra Barthuly

Cassandra is a writer with over five years of experience. Her areas of expertise include food and drink, health and wellness, and digital marketing.
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