BMR and Weight Loss

By Nutrition Expert – Trupti Gurav,Mumbai

Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic . The basal metabolic rate (BMR) and calorie calculator is an excellent tool for working out how many calories your body needs on a daily basis depending on the amount and intensity of your exercise regime.

BMR is the total number of calories that your body needs to perform basic, life-sustaining functions. These basal functions include circulation, breathing, cell production, nutrient processing, protein synthesis, and iron transport [1]

Factors that affect Your BMR

Your BMR is influenced by multiple factors working in combination, including: [3, 4]

  • Body size – larger adult bodies have more metabolising tissue and a larger BMR. Those with bigger bodies have a larger BMR because they have larger organs and fluid volume to maintain.
  • Muscle mass– The amount of muscle tissue on your body. Muscle requires more energy to function than fat. So the more muscle tissue you carry, the more energy your body needs just to exist.
  • Amount of lean muscle tissue – Muscle burns calories rapidly.
  • Amount of body fat – fat cells are ‘sluggish’ and burn far fewer calories than most other tissues and organs of the body.
  • Crash dieting, starving or fasting – Eating too few calories encourages the body to slow the metabolism to conserve energy. BMR can drop by up to 15 per cent and if lean muscle tissue is also lost, this further reduces BMR.  
  • Age – Metabolism slows with age due to loss of muscle tissue, but also due to hormonal and neurological changes. As you get older, your metabolic rate generally slows. This is because of a loss of muscle tissue and changes to hormonal and neurological processes. During development children go through periods of growth with extreme rates of metabolism.
  • Growth – Infants and children have higher energy demands per unit of body weight due to the energy demands of growth and the extra energy needed to maintain their body temperature.
  • Gender – Generally, men have faster metabolisms because they tend to be larger.
  • Genetic predisposition –Your metabolic rate may be partly decided by your genes.
  • Hormonal and nervous controls – BMR is controlled by the nervous and hormonal systems. Hormonal imbalances can influence how quickly or slowly the body burns calories.
  • Environmental temperature – If temperature is very low or very high, the body has to work harder to maintain its normal body temperature, which increases the BMR.
  • Environmental changes– Such as increased heat or cold force the body to work harder to maintain its normal temperature and increases BMR.
  • Infection or illness – BMR increases because the body has to work harder to build new tissues and to create an immune response.
  • Amount of physical activity – Hard-working muscles need plenty of energy to burn. Regular exercise increases muscle mass and teaches the body to burn calories at a faster rate, even when at rest.
  • Physical activity – Exercise increases muscle mass and powers up your metabolic engines burning calories at a faster rate, even when at rest.
  • Drugs – like caffeine or nicotine, can increase the BMR. Caffeine and nicotine can increase your BMR whilst medications such as antidepressants and steroids increase weight gain regardless of what you eat.
  • Dietary deficiencies – For example, a diet low in iodine reduces thyroid function and slows the metabolism. Food changes your metabolism. What and how you eat has a big influence on your BMR.

How to increase your BMR 

These are some exercises you can do to increase your BMR: [5]

1. Increase your workout with weights:  You can increase your BMR by as much as 7% after several weeks of weight workouts. But you have to lift heavy weights. If you lift weights and have to struggle in the last two reps, you activate more fast-twitch muscle fibres, which are the ones that have the highest strength capabilities. These create a higher metabolic load. It is best to get a personal trainer to show you how to do these weighted workouts at first, then you can do them on your own.

2. Mix cardio exercises and weights: If you mix these up in the same exercise session, you will burn more calories because your oxygen uptake is increased.

3. Do interval training: If you do sprint interval training (for two minutes), studies have shown that this is equivalent to 30- minute endurance training. So you can choose your favourite aerobic exercise (running, cycling, and elliptical trainer) and do intervals of 30 seconds each at high intensity, followed by a minute of low intensity for recovery. That is why workouts like Zumba or Body Combat help burn calories.

4. Stretching: You may not realise it, but stretching your muscles before and after your workout increases your caloric expenditure significantly.

How to calculate the BMR?

Calculating your BMR can be quite a difficult process. The formula used for BMR is different for both sexes.

  • One of the easiest and simplest ways you could calculate your BMR is by using the calculator available online. The result you get will indicate how many calories your body needs to perform some of the most basic functions, such as breathing, digesting food, and doing daily activities.
  • BMR also depends on your physical activity during the day. You have to use an equation for this. One of the most famous formulas for calculating BMR is the Harris Benedict equation. It was developed in 1918.

How to use your BMR to help you lose weight [6]

Weight loss is tricky, but using calculators that factor in your BMR are helpful for taking a more customized approach for your calories and macronutrient needs.

If you want to lose weight, you have to be in a calorie deficit, meaning the calculator will set your daily food intake to equal less calories than what you burn. Sometimes when you take an online quiz to find this number, you will be asked how fast you’d like to lose weight. Then the calorie deficit will be adjusted accordingly. The faster you want results, the more extreme you will have to be with cutting calories. But many experts say that slow and steady is optimal compared to trying to lose a lot of weight quickly. 

If you want to maintain your weight instead of lose or gain, then knowing your BMR  can help you know how many calories you should aim to consume each day to maintain your weight.

On the flipside of weight loss is gaining muscle mass. This too requires that you strategically approach your nutrition and add calories into your day (likely in the form of protein and carbs) to make sure you can gain muscle. 

References:-

  1. https://www.verywellfit.com/what-is-bmr-or-basal-metabolic-rate-3495380
  2. https://www.healthline.com/health/exercise-fitness/metabolic-age#vs-chronological-age
  3. https://www.inspiredchiropractic.com/10-factors-that-affect-your-metabolism/
  4. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/metabolism
  5. https://www.thestar.com.my/lifestyle/viewpoints/tell-me-about/2013/08/28/understanding-bmr
  6. https://www.cnet.com/health/how-to-find-your-bmr-to-lose-weight/

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