is the body's engine, converting food into energy for life. It's a complex dance of breaking down nutrients and building up essential compounds, all regulated by hormones and enzymes to keep your body running smoothly.
is key to maintaining a healthy weight. When you eat more calories than you burn, you gain weight. When you burn more than you eat, you lose weight. Understanding this balance helps you make smart food and exercise choices.
Metabolism and Energy Balance
Definition and Role in Energy Production
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Metabolism the sum of all chemical reactions occurring within an organism to maintain life
Includes breakdown of molecules to obtain energy ()
Involves synthesis of compounds needed by cells ()
Essential for energy production converts nutrients into usable energy in the form of adenosine triphosphate (ATP)
Regulated by hormones, enzymes, and other factors to maintain homeostasis and ensure efficient energy utilization
Basal Metabolic Rate (BMR)
Represents the minimum energy required to maintain vital functions at rest
Influenced by factors such as age, sex, body composition, and genetics
Catabolism vs Anabolism
Catabolism
Breakdown of complex molecules into simpler ones, releasing energy in the process
Examples: breakdown of glucose during , oxidation of fatty acids during
Catabolic processes are exergonic, meaning they release energy
Anabolism
Synthesis of complex molecules from simpler ones, requiring an input of energy
Examples: synthesis of proteins from amino acids, formation of glycogen from glucose
Anabolic processes are endergonic, meaning they require energy input
Energy Balance
Maintained when energy consumed through food equals energy expended through basal metabolism, physical activity, and
Positive energy balance occurs when energy intake exceeds expenditure, leading to weight gain and potential health issues ()
Negative energy balance occurs when energy expenditure exceeds intake, resulting in weight loss and potential malnutrition if prolonged
Metabolic Pathways for Macronutrients
Carbohydrate Metabolism
Glycolysis: breakdown of glucose into pyruvate, generating ATP and NADH in the cytoplasm
Citric acid cycle (): oxidation of acetyl-CoA derived from pyruvate, fatty acids, and amino acids in the mitochondrial matrix, producing NADH, FADH2, and ATP
and oxidative phosphorylation: generation of ATP through the transfer of electrons from NADH and FADH2 to oxygen in the mitochondrial inner membrane
Gluconeogenesis: synthesis of glucose from non-carbohydrate precursors (amino acids, glycerol) in the liver and kidneys
Lipid Metabolism
Beta-oxidation: breakdown of fatty acids into acetyl-CoA in the mitochondrial matrix, generating NADH and FADH2 for ATP production
: formation of ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) from acetyl-CoA in the liver during periods of low carbohydrate availability or prolonged fasting
: synthesis of fatty acids from excess acetyl-CoA, primarily in the liver and adipose tissue, and their storage as triglycerides
Occurs when energy intake exceeds expenditure
Protein Metabolism
: transfer of an amino group from an amino acid to an alpha-keto acid, forming a new amino acid and alpha-keto acid
: removal of the amino group from an amino acid, generating ammonia (converted to urea) and an alpha-keto acid that can enter the citric acid cycle
: amino acids that can be converted to glucose through gluconeogenesis (alanine, glutamine)
: amino acids that can be converted to ketone bodies (leucine, lysine)
Factors Influencing Energy Balance
Dietary Factors
Macronutrient composition (carbohydrates, proteins, fats) and caloric content of food influence energy intake and balance
High-fat and high-sugar diets can lead to excessive energy intake and weight gain
Physical Activity and Exercise
Regular exercise increases energy expenditure, helps maintain a healthy body weight, and improves overall metabolic health
Sedentary lifestyle contributes to reduced energy expenditure and increased risk of obesity
Hormonal Regulation
Hormones such as , , , and play crucial roles in regulating appetite, energy storage, and utilization
Insulin promotes glucose uptake and storage, while glucagon stimulates glucose release from the liver
Leptin signals satiety, while ghrelin stimulates hunger
Hormonal imbalances can contribute to obesity and metabolic disorders (type 2 diabetes)
Genetic and Environmental Factors
Variations in genes involved in metabolism, appetite regulation, and energy expenditure can influence an individual's susceptibility to weight gain or obesity
Environmental and social factors (access to healthy food options, socioeconomic status, cultural influences) can impact dietary choices and energy balance
Imbalances in energy metabolism can lead to increased risk of cardiovascular disease, certain cancers, and other health problems
Maintaining a healthy energy balance through a balanced diet, regular physical activity, and managing stress is crucial for optimal health and disease prevention