Metabolic Factors That Influence Basal Metabolic Rate

Abstract

Basal metabolic rate (BMR) or fasting heat production (FHP) is most simply defined as the energy needed to sustain life in an organism. Over the years many people have come up with many ways to calculate, estimate, and predict BMR in different species based on different variables. Some of the arguably more important names in this field are; Brody, Kleiber, and Blaxter. These men helped revolutionize the field of nutritional energetics. From them came the powerful equation; FHP = 77BW0.75 (although some may argue the exponent, 0.75 is most widely accepted today). This paper will look at the metabolic factors that go into determining BMR such as various body tissues and their energetic contributions, uncoupling proteins that are found in various tissues throughout the body, and ways to either increase or decrease one’s BMR and the resulting effects whether in humans as weight loss or in livestock as weight gain.

Introduction

Basal metabolic rate (BMR) or fasting heat production (FHP) is basically the energy that is needed for the body to be alive or exist at rest. BMR can be estimated many different ways; indirect calorimetry via mouthpieces, ventilated hoods, or respiration chambers or equations that have been developed over many years of research. The better known of these equations include: FHP = 77*BW0.75 (which is Kleiber’s equation adapted from the exponent 0.756 and Brody would argue the exponent should be 0.734) and the Harris-Benedict Equations;

For men, BMR = 66.5 + (13.75 x W) + (5.003 x H) - (6.775 x A)

For women, BMR = 655.1 + (9.563 x W) + (1.850 x H) - (4.676 x A)

In these equations; W = weight in kg, H = height in cm, and A = age in years. According to the Harris-Benedict Equations, you can see that age negatively affects BMR. These three equations are just a few of the many that can be used. FHP = 77* BW0.75 is criticized by many people for not bringing in other variables that can play a part such as; level of alimentation...