If weight management is a goal of yours for the New Year, it may be helpful to review the basic components of the energy balance equation. The most common unit of energy measurement in the field of nutrition is called the Calorie or kilocalorie (kcal). Lasting changes in body weight are determined by the number of kcal “in” vs. kcal “out”.
The energy intake side of the equation consists of four major components: carbohydrates, lipids, proteins, and alcohol. Carbohydrates in the form of sugar and starch contain 4 kcal/gram. Lipids from animal fats and vegetable oils contain 9 kcal/gram. Proteins from meat or beans contain 4 kcal/gram. And alcohol in beer and wine contains 7 kcal/gram. Water, vitamins, and minerals do not contain energy (0 kcal/gram). All told, the average American consumes between 1800-2700kcal/day (Source: USDA, 2010).
Although energy intake seems simple and straightforward, there are some “peculiarities” to consider. For instance, fiber is a type of carbohydrate that our bodies cannot digest and therefore does not contain kilocalories (for the most part). Also, while fats and oils are very energy dense (9kcal/gram), they are slow to digest and contribute to a greater sense of satiety than sugar or starch. That means that lipids help keep us fuller longer, and may help prevent cravings in between meals.
The energy expenditure side of the equation consists of three major components: resting metabolic rate (RMR), the thermic effect of food (TEF), and physical activity (PA). RMR is the number of kcal expended at rest and is largely determined by a person’s lean muscle and organ mass. TEF refers to the number of kcals that a person expends to digest and absorb food. PA refers to the number of kcal expended above and beyond RMR and TEF; it can vary from several hundred kcal/day to several thousand kcal/day. For a moderately active person, total daily energy expenditure (RMR + TEF + PA) may range from 1500kcal to 2500kcal.
Calories and weight management
With regard to weight management there are approximately 3500kcal per pound of body fat – although the exact number of kcal in a pound body fat varies significantly between people (see previous posts). Thus, if you would like to lose one pound of body fat you’ll need to create a deficit of 3500kcal. Despite the quickness and ease with which diet books and advertisements claim to create this deficit, hopefully you know better. Consider for one that a 150lb person expends approximately 100kcal to walk or run a mile and you’ll realize that losing/maintaining weight takes considerable focus and effort. It certainly can’t happen overnight!
Food for thought
Next week we’ll discuss the most common pitfalls or mistakes that people make when attempting to lose weight. In the meantime, what do you think the three most common pitfalls are?