Energy Balance

Energy Intake

Energy intake is the amount of energy, expressed as calories, supplied by the diet. When you consume foods and beverages, calories created by the digestion of carbohydrates, fats, and proteins provide the body with energy to help it function optimally. Carbohydrates and proteins contain 4 calories per gram, and fats contain 9 calories per gram.

Although alcohol is another dietary source of calories or energy for the body, it contains few key nutrients to keep us healthy. One gram of alcohol contains 7 calories.

Factors That Affect Energy Intake

How many calories we consume on any given day is affected by an interaction of our genetic makeup and the environment we are exposed to early in life and our adult years. Hunger is a basic sensation that drives us to eat. The foods and beverages we prefer to consume are determined by genes and exposure to foods and beverages early in life. The sight and smell of foods or beverages influence our appetite; highly palatable and appealing foods such as sweets or fried foods can increase appetite and lead us to eat (even if we’re not hungry), while the sight or smell of some foods can diminish appetite.

Other factors that affect our energy intake include: Nutrients in food, Portion sizes, Psychological factors and Social factors.

Foods that high in protein (for example, lean meats, poultry, fish, soy foods, nuts and seeds, and low-fat dairy foods), fiber (for example, fruits, vegetables, and whole grains), or both (for example, beans) promote satiety, by filling us up more than foods that are lower in protein or fiber.

Portion sizes also influence how much we eat and drink. Often, we consume more when we’re served larger portions than when we are presented with smaller portions. Because many people eat many of their meals away from home and foods and beverages (whether from restaurants, food carts, or vending machines, for example) are offered in bloated portion sizes, it’s no surprise that many of us consume more than we intend to without even realizing it and subsequently gain weight.

Overweight and Obesity

Emotions such as stress or anxiety can also affect energy intake. Some people eat more when feeling down; others might shun or dramatically decrease food intake in response to negative emotions. Also, those who tend to eat more when they’re stressed often turn to high-calorie, high-fat, or high-sugar but nutrient-poor “comfort foods” to make themselves feel better (even though these foods actually may do the opposite and make them feel worse, promote swings in their blood sugar levels, increase hunger, or contribute to overeating and subsequent weight gain).

Dining with others can encourage people to eat more than they would if they were alone. However, eating in front of the television or computer monitor, while listening to music, while driving, or when otherwise distracted can lead to mindless munching.

Energy Expenditure

Energy expenditure is the amount of calories the body burns or uses up each day. Basal energy expenditure (BEE) counts the calories used just for breathing and other basic body functions. It accounts for a surprising 75% of the total calories you burn each day. Total daily energy expenditure additionally includes the energy used to

• Process food (this include digesting and absorbing food, moving nutrients around the body, and storing nutrients for later use; represents about 10% of total energy expenditure)
• Support physical activity and exercise (this include all body movements, varies from person to person and depends on the type of activities you choose and how often, how intensely, and for how long you engage in physical activity or exercise)

Factors That Affect Energy Expenditure

Although genes largely determine whether your resting metabolic rate (RMR) is high or low, several environmental factors affect how many calories you burn each day. RMR is relatively consistent in an individual but can vary widely from person to person; this accounts for the marked differences in individual daily calorie needs.

Estimating Your Daily Calorie Needs

Those who have more lean body mass have a higher RMR than those with a lower proportion of lean body mass, which means they burn more calories. Men often have a higher RMR than women because they tend to weight more and have more lean body mass. Younger people also tend to have a higher RMR than older people because getting older often causes a loss of muscle tissue and an increase in body fat. RMR might also increase during

• Growth (example: pregnancy, infancy, and childhood)
• Cold weather (RMR increases to warm the body)
• Physical stress, illness, or fever

Daily calorie expenditure can also vary tremendously among individuals because of body movements not related to exercise. Nonexercise activity thermogenesis (NEAT) is the energy expended during daily activities such as sitting, standing, and fidgeting. Studies have shown that lean people expend more energy on these subtle body movements than obese people.

Hunger is a painful or unpleasant sensation in your stomach caused by the lack of food.

Appetite is a mental desire for food that might have nothing to do with hunger; it often results from pleasant sensations associated with foods or can even be triggered by the time of day or by smells.

Satiety is a feeling of fullness (satiation) that occurs after you have eaten enough; this sensation reduces the desire for more food.

Basal energy expenditure (BEE), also called resting energy expenditure (REE), is the energy or calories needed by the body to support basic physiological functions such as breathing, moving blood around the body, and building and repairing body cells. BEE accounts for most of the total energy used by the body each day and is fairly constant.

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