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Author : Aditya Mahajan, INFS faculty

Keywords: Metabolism, BMR, TDEE, Calories, Fat loss Everybody at some point must have heard the term ‘metabolism’ or you must have heard someone saying my metabolism is slow -I can-not lose weight easily or my metabolism is fast- I am unable to gain weight. So what is metabolism? This article will cover it up. But first let’s recall the major rule of weight loss/gain is that the changes in your bodyweight reflects your calorie balance. If you eat more calories than you burn then you will gain weight. Likewise, you will lose weight if you intake fewer calories. This is very important to understand the concept of metabolism. Components of Metabolism: Put simply your metabolism doesn’t exist in isolation. It’s a combination of genetic, environmental and other elements of your biology. So, there are three components of metabolism 1)Basal Metabolic Rate (BMR): You burn calories all day and night even if you do nothing but sleep or watch TV. Most of the calories spent each day are for breathing, circulation, maintaining your body temperature, moving compounds in and out of cells, and other normal body processes you rarely need to think about. Your BMR depends on follwing things: Body composition Body size Age Gender Hormones: Dieting and starvation 2)Thermic Effect of Food (TEF): It is the energy-cost associated with the digestion and related processing of the food. TEF is influenced by several factors such as body composition, meal composition, nutrition profile etc and roughly account for 6-12% of TDEE. (Total Daily Energy Expenditure) 3)Activity thermogenesis (AT): This is the most variable component of your metabolism. AT comprises 2 components: Energy expenditure of exercise: It represents the calories burned during an exercise or sports. For sedentary individuals, energy expenditure of exercise is zero. Even for the majority of the exercisers, exercise related energy expenditure is still very small (<100Kcals/day on average). Non-Exercise Activity thermogenesis (NEAT): NEAT accounts for energy expenditure for activities that aren’t formal exercise. It includes taking the stairs, dancing, cleaning house etc. NEAT can vary upto 2000Kcals/day between different people. This even explains why some people lose fat quicker, when on a diet, than others. Probably their NEAT is higher than the rest. Calorie Math And Why It’s Dynamic? Our body is basically a biological machine and like every other machine, it follows laws of thermodynamics as well. We intake energy in the form of food and do physical work to utilize that energy. However, it’s not always simple mathematics of calories in=calories out. The energy balance equation is complex and dynamic with numerous feedback loops and one side of the equation influences the other side Excerpt from a chapter in upcoming INFS Health Series for Slow metabolism – which will be released very soon! ABOUT INSTITUTE OF NUTRITION AND FITNESS SCIENCES Institute of Nutrition and Fitness Sciences (INFS) was established with the intent of providing comprehensive and practical knowledge in Health and Fitness. INFS Nutrition and Training courses are divided into levels so that everyone from a general health enthusiast to someone who wants to build a career in Fitness industry can benefit from them. For more information about our Nutrition and Fitness courses please visit
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