The number one goal of 90% of my clients has been weight loss. Some people are obese and need to lose a substantial amount of weight for health reasons and other people with a healthy BMI just want to get rid of a few pounds to look and feel better (we all want six pack abs). Weight loss depends on how much energy is used to do work (i.e., to move, digest food, think etc.,) relative to how much energy is consumed and stored (caloric intake). Energy is constant so if the energy output (work done) is greater than the energy input (calories consumed) there will be a negative energy balance which forces the body to tap into fat to make up for that deficit. The energy output consists of a person’s resting or basal metabolic rate (BMR), which is the total number of calories a person uses while at rest, and a person’s active metabolic rate (AMR), which is the total number of calories a person uses if they incorporate movement. If you want to lose fat then you have to create a daily negative caloric balance by limiting your caloric intake or increasing your BMR and AMR or a combination of both.
There are several factors that influence the BMR, AMR and the rate of weight loss. The BMR is influenced by body composition, age, gender, level of stress, body type (or somatotype), hormones and food intake. The AMR is influenced by the activity level. A negative energy balance is created by controlling the caloric intake. All of these need to be carefully balanced in order to achieve your weight loss goal without compromising your health or losing muscle.
The higher the percentage of body fat the quicker the rate of weight loss. I’ve trained obese people around 40% body fat who could shed up to 3lbs a week by following a rigorous program. However if you are around 15% body fat then the rate of weight loss is exponentially lower. At you’ll be extremely lucky to lose 1 pound per week (the typical amount is 0.5lbs/week). Having a higher percentage of muscle also contributes to quicker fat loss but not as much as many people claim. The common misconception is that muscle is 20x more metabolically active than fat and therefore having more muscle raises your BMR accordingly. Recent studies found that 1 pound of muscle burns about 6 calories per day, not 50 calories as is popularly believed. This is still higher than fatty tissue which burns 2 calories per pound per day.
A person’s age and gender also influence the rate of weight loss. As you get older your metabolism slows down because your body tends to lose muscle and gain fat which slows down your ability to burn calories. However this can be attenuated by doing regular cardio, strength training and keeping a healthy diet. There is a slight difference between men and women because men have more testosterone which helps to build muscle and so men will have a higher BMR than women on average because they have more muscle.
The level of mental and physical stress affects the rate of fat loss. Cortisol is a hormone released when the body is under stress such as in a fight or flight situation. It serves a biological function of freeing up energy by breaking down fat and muscle tissue Revitaa pro during a stressful event so that the body can use it to fight or flee. However, in today’s society we do not use that energy to fight or flee and so it gets deposited back into fat around the abdominal region. Prolonged stress can increase the resting level of cortisol making it very hard to burn fat in the abdominal region.
Humans come in three different body types or somatotypes that are genetically determined: ectomorph, mesomorph and endomorph. These body types represent a continuum of body composition and the ability to gain or lose weight (either muscle or fat). Ectomorphs have the least total body mass (made up of fat, muscle and bone). Ectomorphs tend to be tall and skinny and have difficulty gaining weight because they have a fast metabolism. Weight loss for ectomorphs is not an issue but muscle gain is. Mesomorphs have an average total body mass and can change their body composition very easily. Mesomorphs have an intermediate metabolic rate. Endomorphs have the greatest total body mass and tend to put on weight very easily. Endomorphs have the greatest difficulty in burning fat because they have the slowest metabolism.
The BMR is influenced by the levels of thyroid hormones and the catecholamines epinephrine and nor-epinephrine. Thyroid hormones are thermogenic raising body temperature and BMR. People with hypothyroidism (low level of thyroid hormones) have a very slow metabolism, tend to put on fat very easily and have difficulty losing fat. People with hyperthyroidism (high level of thyroid hormones) have a very fast metabolism, tend to be skinny and have difficulties putting on weight. The sympathetic nervous system is responsible for arousal and utilizing energy to be used in times of stress or arousal. The primary hormones that activate the sympathetic nervous system are epinephrine (adrenaline) and nor-epinephrine. Both of these hormones will increase heart rate and force of contraction, increase blood flow to muscles, suppress hunger, and utilize the body to break down fat and glycogen to produce glucose. Most weight loss pills are stimulants that increase the activity of the sympathetic nervous system. Caffeine is often used in over the counter weight loss pills in conjunction with other stimulants because it increases cardiac output, helps the body to utilize fat as a fuel source by increasing epinephrine levels, and suppresses hunger.
Food intake has the greatest effect on basal metabolic rate. The body has to expand energy when digesting and processing food. This is called the thermic effect of food or diet induced thermogensis. The quantity and type of food ingested influences how much energy is required to process the food. Research indicates that proteins are harder to process than fats and so have a much higher thermic effect. Therefore increasing the quantity of protein in your diet will raise your BMR. Foods that are high in fiber such as celery and grapefruit are the hardest to process and have the highest thermic effect. These foods also have what is called a negative caloric balance because they take more energy to digest than the energy they release from digestion.
Increasing the level of physical activity increases the AMR. The more active you are the more calories are needed. The type of activity you engage in as well as the duration and intensity of that activity influences how many extra calories are needed and from what food source these calories come from.