NASM CNC Chapter 5: Energy Balance and Metabolism

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Chapter Goals:

• Explain thermodynamics.
• Define what an energy balance is.
• Know the factors of energy out and energy in. 
• Be able to explain the energy systems 

Introduction

Metabolism is the chemical process occurring in living organisms that give us energy. Metabolism is a key feature distinguishing life from non-life. Energy production through metabolism will give us a constant supply of energy needed to sustain human life at rest, in physical activity, and during recovery times.

The sun is the provider of the main source of energy needed for life on earth. The solar energy it gives off will go to plants and be used as chemical energy in the process called photosynthesis. The plant will then make into animals, which we will use it.

ATP is the compound of energy that we use. It drives muscle contractions, transmits nerve impulses, and most other amazing chemical reactions that occur in the human body. 

TDEE stands for the total daily expenditure, and this is a calculation of the estimated calorie needs for us. This number of calories someone needs in a day will depend upon the person’s age, the thermic effect of feeding, resting metabolic rate, thermogenesis not from exercise, sex, height, weight, and level of physical activity. The base calculation we always use is simply 2,000 calories per day. This is what the majority of nutrition labels will be based upon.

Thermodynamics

Thermodynamics describes the relationship there is between energy and heat and their conversion from one to another. This energy is in the form of mechanical, electrical, or chemical. 

Human metabolism converts food into heat, work, and stored energy. Calories are consumed By the body, then broken down into smaller pieces, and then they are stored or used for movement. 

The first law of thermodynamics is the law of the conservation of energy. This law states that energy can be transferred from one form to another but can never be destroyed. 2,500 calories consumed will always represent 2,500 calories and be used in some way by the body.

Maintaining Energy Balance

Energy balance is self-explanatory. It is the balance of the calories that we consume minus the calories we burn. 

Energy In represents the energy intake within a certain amount of time.

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Energy Out represents the energy we expend during a certain time. 

The rise in obesity and being overweight results from an energy balance that favors a surplus, thus, people are storing more calories in their bodies. They are not spending enough to keep the balance.

Components of Energy Out

These are the calories we expend. We have four main components of this:

• Resting metabolic rate: 60 – 75% 
• Thermic effect of feeding: 10%
• Thermic effect of activity thermogenesis: 15 – 30%
• Non-exercising activity thermogenesis
• Resting Metabolic Rate

This refers to the total amount of calories that are burned when the body is at complete rest. Some people may refer to this as the basal metabolic rate. The basic functions included here are breathing, circulation, organ function, and also basic neurological function. Everyone has a different RMR; some may be high or some low. The amount of lean body mass, thyroid production levels, and some other slight factors will affect this. 

Thermic Effect of Food

This is basically the increase in energy expenditure after someone takes in a meal. This accounts for the energy needed for the digestion of food.it is about 10% of our daily expenditure.

Thermic Effect of Activity

This is the most variable part of the expenditure as it depends upon what you do throughout the day. It can account for 15 – 30$ of expenditure, which can vary greatly. It includes physical work, muscular activity, and planned exercise events. 

Non-Exercise Activity Thermogenesis

This is seen as everything we do besides sleeping, exercising, or eating. Walking to and from events is a typical big part for people. It can also vary greatly depending on someone’s job. 

Sleep

Sleep deprivation, the restriction of metabolism, and the start of weight gain that accompanies is not well understood yet. The thought is that when you do not sleep enough, your RMR the next day is reduced, and you intake more energy than normal. An easy recipe for weight gain. We need to have a regular sleep schedule that achieves more than 5 hours of sleep. 

Hormones

Hormones regulate our metabolism through many different effects. We will discuss the main ones here.

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Thyroid Hormone

Thyroid hormones work to regulate our metabolism and control our essential growth and development steps.

The thyroid hormone stimulates our metabolism through increases in oxygen consumption and the rate of breaking down ATP. 

The thyroid hormone works to stimulate both lipogenesis and lipolysis. 

It also works for stimulating all aspects of carb digestion.

Cortisol

This is typically called the stress hormone, as they are produced in the adrenal glands as a response to stress. It leads us to increase our heart rate, blood pressure, and elevated glucose levels. 

Testosterone

This hormone is a key hormone for the metabolism of all three macronutrients. It is major in our bodies’ fat composition and muscle mass. It helps to control many pathways in glycolysis, glycogen synthesis, and lipid or cholesterol metabolism.

Components of Energy In

This is the number of calories we take into the body

Appetite

We have a few different factors influencing our appetite:

• Our activity level
• Some social factors
• Leptin and ghrelin production
• The food currently in the stomach
• Environmental Factors

This includes factors like cultural and psychological influencers, economic status, level of education, past experiences you have had, usual portion size, and the palatability of food.

Any disturbance in these systems may negatively affect energy balance, and most often, this is in the form of gaining weight. 

Psychological Factors

The distress of the psychological type will alter eating behaviors slightly. 

Here are some ways that people can practice mindful eating. These can help in times of stress and really any time.

• Eat when you actually are hungry, not just bored.
• Do not let your emotions control your eating habits.
• Engage all six of your senses.
• Make sure to eat in moderate portions.
• Savor small bites of food while you eat.
• Eat slower than normal.
• Chew your food very thoroughly.
• Do not skip any meals throughout the day.
• Individual Variation
• The factors that cause these many variations are:
• Body composition
• Low calorie diets
• Age
• Brown Fat
• Food allergies
• Processing of food
• Caffeine
• Hypothyroidism
• Caffeine
• Lifestyle habits

Food processing

This is defined as anything altering the food’s original form, like drying, freezing, milling, canning, mixing, and adding salt, sugar, fat, or other additives. Food processing changes the chemical and physical nature of our food.

Processing food may make it safer, tastier, or more stable, but it is not without consequences. 

Metabolic Energy Systems

The body needs the energy to fuel itself and to function in all of the physical activity we do. The energy is utilized in the body by different systems that come into action at various times and we should understand these systems.

Energy Transfer

The carbs, protein, and fats get broken down into the simplest form of digestion. These macronutrients are used for biosynthesis, detoxification, thermogenesis, ion transport, and muscle contraction.

We have three main energy systems we use:

ATP – PC System

This is the first pathway that the body uses when starting physical activity of any kind. We also refer to this as the phosphagen system. This pathway uses energy released from the breakdown of phosphocreatine for immediate use, and then it uses the phosphate molecule to make more ATP. It is held in the muscles in a pretty limited supply. The ATP – Pc system is our quickest way to resynthesize ATP, but it is limited to seconds. This system fatigues very fast compared to the other systems. The system that takes over next is the glycogen system. 

Anaerobic (Glycolytic) Energy System

This system provides energy for medium to high intensity bursts of activity. This is usually from 10 seconds to around two minutes of time. Glycolysis literally means the breakdown of glucose. The glycogen that is used is the glycogen found in the blood or the stored glycogen in the muscles. So, ATP is formed rapidly and without the need for oxygen.

End-product of Glycolysis

The end product is pyruvate. This is either transported and used to support more energy production through the Krebs cycle or converted into lactic acid. 

Aerobic Energy System

This energy system is used much more than the other two. This is because it is used for low intensity or simply endurance activity. This lasts from two hours to some hours. This system requires oxygen, unlike the other systems, and it takes a lot more time to overload. We keep a lot of energy for this system in reserves compared to the things used in the other two systems. Some sports that make use of the system are things such as swimming, running, and cycling. The main fuel being used here would be fats and carbs. As the body reaches max effort, the main macronutrient being used is carbohydrates. 

The Krebs Cycle and Electron Transport Chain

The aerobic system includes both the electron transport chain and the Krebs cycle. Both of these use blood glucose, glycogen stores, and plasma-free fatty acids or triglycerides to resynthesize ATP using the mitochondria.