Calories and Energy in Food
What is a Calorie?
Calories are units of energy. In techno-speak, 1 calorie is defined as the amount of energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius (or 1.8 degrees Fahrenheit). Calories are the units we use to measure the energy content of food, except that when appearing on food labels they may also be listed as "kilocalories" (kcal). But don't worry, a kilocalorie is just another name for calorie. Another unit of food energy is the "joule". One calorie is equal to 4,184 joules, and one kilojoule (kJ) equals 1,000 joules.
How Are Calories Related to Weight Control?
If our energy intake (that is, the calorie-content of the food we eat) exceeds our energy expenditure (that is, the calories we burn while at rest and while moving), our body stores the surplus energy as body fat. Result? We gain weight.
How Many Calories Equals One Pound of Body Fat?
Dietitians usually reckon that 3500 calories is equal to one pound of body fat. Therefore, in order to reduce weight (eg. 1 pound per week), each day we need to consume 500 fewer calories than we burn. During a 7-day period, our calorie deficit will amount to 3500 calories. However, it's not essential to achieve these calorie savings exclusively by eating less. We can also increase our calorie expenditure by exercising more. We might eat 250 fewer calories per day and burn an extra 250 calories in aerobic exercise.
What is a Calorie-Controlled Diet?
A calorie-controlled diet is no more than an eating plan with a calculated calorie content. A very-low-calorie diet (or very-low-energy diet, VLED) typically contains about 800 calories per day. It is usually a combination of real food and meal-replacement shakes or bars, and is commonly used under medical supervision by very overweight or obese dieters, with nutritional supplements. A low-calorie eating plan, generally used as a weight loss diet, usually contains 1200-1600 calories. Low-calorie meal recipes (eg. Weight Watchers "Smart Ones" or Lean Cuisine) typically average about 400 calories. High calorie diets, used by athletes and sportspeople who burn very large amounts of energy, may contain up to 10,000 calories.
How Many Calories Do We Need To Eat Each Day?
Our daily calorie requirements depend on a number of factors, including our: gender, age, weight, and level of activity. Very approximate ballpark calorie needs for average sized adults, aged 30, with a sedentary lifestyle, would be 2400 calories (men) or 1800 calories (women). Daily calorie needs for children and teenagers range from 1200 to 2000 calories. For more information about energy requirements, see resources at the top of this page.
How Do I Know How Many Calories I Am Eating?
When it comes to counting calories to determine energy intake, a useful method is to keep a food journal for about 7 days. Each day, list all the food and drink you consume (together with serving size), then add up your weekly total. To find the calorie-content of individual foods, either check the food label or see below for our list of Calories in Foods.
What Are Sensible Ways To Reduce Calories In Our Diet?
As a rough guide, the first step to reducing calories is to avoid calorie-dense foods that are high in fat or sugar. Why avoid these foods? Because they are too easily eaten. For example, after a main meal we are not typically hungry, yet it's easy to demolish a large helping of rich ice cream, or a creamy dessert. By comparison, it's much more difficult to eat 4-5 large apples. In addition, fat contains more than twice the calories (9 per gram) than carbs or protein (4 per gram), while too much sugar may raise blood-glucose levels too fast and leave you hungry within a couple of hours. Another way to make healthy calorie savings (and still feel full) is to choose high fiber foods, such as vegetables, fruits, beans and whole grains. Foods rich in fiber (soluble or insoluble) take longer to digest and give us a sense of satiety.
Are All Calories Equal?
Although scientifically speaking all calories are equal in energy terms, most dietitians and nutritionists advise us to make calorie savings by choosing nutrient-dense foods (meaning food with a high nutritional content) in preference to empty calorie foods (meaning food which contains calories but little or no nutrition). Nutritious foods include: lean meat, fish, low-fat dairy foods, eggs, beans, whole grains and of course plenty of fruit and veggies. Empty calorie foods include: regular sodas, candy, sweets, cakes and cookies. Paradoxically, some high-calorie foods (eg. oily fish) should be preferred to lower calorie options, because of their omega-3 fat content, which is believed to assist metabolic function rather than lead to weight gain.
What Exercise is Best For Calorie-Burning
In general, aerobic exercise (sustained exercise of the large muscles) such as brisk walking, swimming, jogging, running, and treadmill workouts tend to burn the most calories. However, resistance training (eg. weight training) is essential to build muscle and raise your basic metabolic rate. This is because muscle requires more calories to sustain than fat. So the more muscle we have, the more food we can eat before we gain weight.