This month we will dive into some of the science surrounding how we create energy and how food is involved in our energy production. We won't get too in-depth and will keep it simple. Gaining knowledge around how nutrition plays a role in our energy production is key to understanding metabolism and creating healthy habits.
Let's first go to the basics. Yes, Digestion.
Digestion is the process by which the body breaks down food into smaller molecules that can be absorbed and used for energy. The process of digestion begins in the mouth, where food is mechanically broken down by chewing and mixed with saliva, which contains enzymes that start to break down carbohydrates. The chewed and partially digested food, known as bolus, is then swallowed and travels down the esophagus to the stomach via peristalsis.
In the stomach, the bolus is mixed with gastric juice, which contains hydrochloric acid and the enzyme pepsin. Pepsin breaks down proteins into smaller peptides, and the acid helps to kill harmful bacteria and denature proteins, making them easier for enzymes to break down. The stomach also has strong contractions that grind the food into a paste-like consistency called chyme.
The chyme then travels through the pyloric sphincter and into the small intestine. The small intestine is where most of the absorption of nutrients takes place. The walls of the small intestine are lined with villi and microvilli, which increases the surface area available for absorption. The small intestine also secretes enzymes such as pancreatic amylase, trypsin, and lipases, which break down carbohydrates, proteins, and fats, respectively. Additionally, bile, which is produced by the liver and stored in the gallbladder, is released into the small intestine. Bile helps to emulsify fats, making them easier for enzymes to break down.
The broken-down nutrients are absorbed through the walls of the small intestine into the bloodstream and then transported to the liver.
The liver detoxifies the absorbed nutrients and releases them into the bloodstream for distribution to the rest of the body. Anything not absorbed in the small intestine continues its journey to the large intestine. The main functions of the large intestine are to absorb water and electrolytes, and to form and eliminate feces. The feces are then eliminated through the rectum and anus.
Overall, digestion is a complex process that involves multiple organs and enzymes to break down food into smaller molecules that can be absorbed and used for energy by the body.
Calories are a unit of measurement for energy. The body obtains energy from the food we eat in the form of calories, which are then used for various bodily functions such as maintaining body temperature, supporting physical activity, and supporting organ function. The process by which the body converts food into energy is called metabolism.
When we eat, our body breaks down the food into molecules that can be used for energy. Carbohydrates, fats, and proteins are all broken down into smaller molecules that the body can use. Carbohydrates are broken down into glucose, the body's primary energy source, while fats are broken down into fatty acids and glycerol. Proteins are broken down into amino acids.
Once these molecules have been broken down, they enter the bloodstream and are transported to cells throughout the body, where they are used to produce energy. The process by which glucose is converted into energy is called cellular respiration, which occurs in the mitochondria of cells. During cellular respiration, glucose and oxygen are combined to produce carbon dioxide, water, and energy in the form of ATP (adenosine triphosphate). Overall, the body's metabolism converts calories from food into energy for the body's functions through a series of chemical reactions.
The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle, is a series of chemical reactions that occur in the mitochondria of cells and is an essential part of cellular respiration. The Krebs cycle is the second stage of cellular respiration, following glycolysis, in which glucose is broken down into pyruvate.
The Krebs cycle starts with the conversion of acetyl-CoA, a molecule derived from pyruvate, into citrate. This begins a series of reactions in which citrate is broken down into smaller molecules, releasing energy in the form of ATP and other forms of energy, such as NADH and FADH2. These molecules then go through the Electron transport chain and produce ATP through oxidative phosphorylation.
During the Krebs cycle, carbon atoms are removed from the original acetyl-CoA molecule in the form of CO2. These carbon atoms are then used to produce ATP, NADH, and FADH2, which are used in the next stage of cellular respiration, the electron transport chain.
In summary, the Krebs cycle is a series of chemical reactions that occur in the mitochondria of cells, which converts acetyl-CoA into smaller molecules, releasing energy in the form of ATP and other energy forms then used in the Electron transport chain to produce more ATP.
ATP (adenosine triphosphate) is the primary energy currency of the cell, meaning it is the main molecule used to transfer energy within cells. ATP is made up of adenine, a sugar called ribose, and three phosphate groups.
ATP is created through a process called cellular respiration, which occurs in the mitochondria of cells. In cellular respiration, glucose and oxygen are combined to produce carbon dioxide, water, and energy in the form of ATP. This process can be broken down into three stages: glycolysis, the Krebs cycle, and the electron transport chain.
Glycolysis is the first stage of cellular respiration, in which glucose is broken down into pyruvate. The second stage is the Krebs cycle, in which pyruvate is broken down further, and energy is released in the form of ATP and other forms of energy, such as NADH and FADH2. The final stage is the electron transport chain, where the energy from NADH and FADH2 is used to produce more ATP.
The main source of fuel for the production of ATP through cellular respiration is glucose which is obtained from the carbohydrates present in food. But not only carbohydrates, fats and proteins can be broken down to generate glucose or molecules that can be converted to glucose, and used in the cellular respiration.
It's worth noting that the body is able to store glucose in the form of glycogen and use it as needed, but when glycogen stores are depleted the body can break down fats and proteins to make glucose, this process is called gluconeogenesis.
There are several ways to measure the amount of energy (calories) that a person is exposed to, including:
Diet diary: Keeping a food diary, where you record everything you eat and drink throughout the day, can be a helpful way to measure your energy intake.
Caloric intake calculation: You can also calculate your caloric intake by using information on the nutrition labels of the foods you eat, or by using online tools or mobile apps that provide calorie information for different foods.
Metabolic rate: Measuring the number of calories you burn at rest, known as basal metabolic rate, can provide an estimate of your energy expenditure. This can be done using a metabolic cart, which measures the amount of oxygen you consume and the amount of carbon dioxide you produce.
Physical activity measurement: Wearing a fitness tracker or activity monitor can measure the amount of energy you expend during physical activity.
Body Composition measurement: Body composition can be measured by various methods such as bioelectrical impedance analysis (BIA), dual-energy x-ray absorptiometry (DXA), and skinfold thickness measurements. These measurements can give an estimate of the amount of body fat and lean mass, which can be used to estimate energy requirements.
Energy Balance: Energy balance is the relationship between energy intake and energy expenditure. When energy intake is equal to energy expenditure, a person is in energy balance. When energy intake is greater than energy expenditure, a person is in positive energy balance and will gain weight, and when energy intake is less than energy expenditure, a person is in negative energy balance and will lose weight.
It's important to note that measuring energy exposure is not an exact science, and different methods may yield slightly different results.
The body's organs and systems that burn the most calories and require the most energy are those involved in maintaining basic bodily functions and physical activity.
The brain: The brain is the most energy-intensive organ in the body, accounting for about 20% of the body's total energy expenditure. The brain requires a constant supply of glucose and oxygen to function properly, and this constant demand for energy is what makes the brain such a high consumer of calories.
The heart: The heart is a muscle that requires a lot of energy to contract and pump blood throughout the body. Physical activity, such as cardiovascular exercise, can increase the heart's energy consumption.
Muscles: Muscles require energy to contract and generate force. Physical activity, especially strength and endurance training, can increase muscle mass, which in turn increases energy expenditure.
The liver: The liver plays a vital role in metabolism and is responsible for many functions, such as detoxifying the body, producing bile, and regulating glucose and lipid levels. All these functions require energy, making the liver a high consumer of calories.
The digestive system: The process of digesting food requires energy. The process of breaking down food and absorbing nutrients requires energy, and the more food you eat, the more energy is required.
Thermogenesis: Thermogenesis is the body's process of generating heat, which also burns calories. Hormones such as norepinephrine and thyroid hormones, as well as certain foods, can increase thermogenesis and energy expenditure.
These are some examples of the body's main energy consumers. The body's energy expenditure is also affected by factors such as age, sex, weight, and muscle mass, among others.
The body's energy systems are the ways in which the body produces energy to fuel its many functions. There are three main energy systems: the phosphagen system, the glycolytic system, and the oxidative system.
Phosphagen system: Also known as the ATP-CP system, this is the body's immediate energy source and is used for short, high-intensity activities such as weightlifting or sprinting. The phosphagen system uses stored ATP and CP (creatine phosphate) to produce energy quickly and without the need for oxygen. However, the phosphagen system can only sustain activity for about 10-15 seconds before it becomes exhausted.
Glycolytic system: Also known as the anaerobic system, this system is used for moderate-intensity activities that last for longer periods of time, such as a 400-meter race or a set of heavy squats. The glycolytic system uses stored glycogen (the stored form of glucose) to produce energy without the need for oxygen. However, as the glycogen stores are depleted, the system produces lactic acid as a by-product, which can lead to muscle fatigue.
Oxidative system: Also known as the aerobic system, this system uses oxygen to produce energy for low-intensity activities that can be sustained for long periods of time, such as a marathon or a long bike ride. The oxidative system uses the oxygen to oxidize glucose and fatty acids, producing energy through the process of cellular respiration in the mitochondria of the cells. This system can sustain activity for extended periods of time, but it takes longer to produce energy than the other systems.
It's worth noting that all three energy systems work simultaneously and in varying degrees, depending on the intensity and duration of the activity being performed. The body will use the phosphagen system first, and then shift to the glycolytic system as the phosphagen system becomes exhausted. The oxidative system will be used as a primary source of energy during steady-state exercise or endurance activities.
It's also worth noting that the body's energy system is adaptable, meaning that over time, with proper training and nutrition, the body can improve its ability to produce energy and become more efficient in using the different energy systems.
Energy balance refers to the relationship between energy intake (the calories consumed through food and drinks) and energy expenditure (the calories burned through metabolism, physical activity, and thermogenesis).
When energy intake is equal to energy expenditure, a person is in energy balance, and their weight will remain stable. However, if energy intake is greater than energy expenditure, a person is in a positive energy balance and will gain weight over time. On the other hand, if energy intake is less than energy expenditure, a person is in a negative energy balance and will lose weight over time.
Energy balance is a crucial concept in understanding weight management and maintaining a healthy weight. To lose weight, a person must create a negative energy balance by consuming fewer calories than they burn or by increasing their energy expenditure through physical activity. To gain weight, a person must create a positive energy balance by consuming more calories than they burn.
It's important to note that energy balance is affected by several factors, including age, sex, weight, muscle mass, and physical activity levels. Additionally, different individuals have different energy requirements depending on their body composition, metabolic rate, and lifestyle.
Measuring energy intake and expenditure can be done through different methods such as diet diary, caloric intake calculation, metabolic rate measurement, physical activity measurement, body composition measurement, and others. By understanding energy balance, a person can make informed decisions about their diet and physical activity to achieve and maintain a healthy weight.
It is important to note that focusing solely on weight as a measure of health can be misleading and may not accurately reflect a person's overall well-being.
Weight can be affected by various factors such as muscle mass, hydration levels, and hormonal changes. Therefore, it is not always an accurate indicator of health. Additionally, placing too much emphasis on weight can lead to disordered eating patterns, body dissatisfaction, and a negative impact on mental health.
Focusing on overall health and well-being rather than just weight is important. This includes not only physical health but also mental and emotional well-being. Achieving a healthy balance in life includes a balanced diet, regular physical activity, adequate sleep, stress management, and a positive mindset.
Additionally, it's essential to understand that weight loss is not always necessary for good health and that a person can be healthy in a variety of weight ranges. Instead, it is more important to focus on healthy behaviors such as eating a balanced diet, engaging in regular physical activity, and maintaining a healthy lifestyle.
Achieving a healthy balance in life and understanding that weight is just one aspect of health can lead to a more positive relationship with food and body and ultimately contribute to a more fulfilling and longer life. It's also important to seek guidance from a healthcare professional or a registered dietitian when making changes to your diet and physical activity to ensure that you are meeting your nutritional needs and following a healthy and sustainable plan.