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Nutrition and Metabolism


What is a calorie?

A calorie is a measurement of energy. A dietary calorie is defined as the energy needed to raise the temperature of 1 kilogram of water by 1 degree Celsius. Fats, protein, and carbohydrates are the three major sources of dietary calories.  Fats contain 9 calories per gram while protein and carbohydrates contain 4 calories per gram. Alcohol, an often ignored calorie source for drinkers, contains 7 calories per gram.

How many calories does a person need daily?

Calories are used to power all the activities of the human body including the thousands of reactions our cells are performing at any given moment, even during our sleep! These calories needed for these reactions come from our diets; daily calorie intake depends on the age, gender, height, weight, physical activities, and the weight target of the person.  A recommended daily calorie intake can be calculated using the Food and Nutrition Calculator developed by GB.  On average, the recommended daily calorie intake for most adults ranges from 1,800 to 2,400 calories.

How do you use calorie restriction to manage weight loss?

When the calories you consume matches the amount of energy you need to power your body, you are in “zero energy balance” meaning your weight will stay constant. When you consume more calories than your body needs, the excess is converted into fat for storage, leading to weight gain in a situation called “positive energy balance”.  When you consume fewer calories than your body needs, your stored fat is broken down to make up for the energy deficit, leading to a weight loss in a situation called “negative energy balance”.

Calorie restriction is an effective strategy to lose weight through creating a negative energy balance. Beneficial effects of calorie restriction include weight loss and associated lower risks for diseases such as cardiovascular disease, type 2 diabetes, metabolic syndrome etc. However, mismanagement of calorie restriction can trigger eating disorders, hormonal changes, and malnutrition etc.

You can calculate your recommended daily calorie intake at the GB Food and Nutrition Calculator depending on your weight goals. The calculators were developed based on the principle that your weight loss is your body fat loss. Each pound of body fat stores roughly 3,500 calories.  In order to lose one pound per week, you would need to create a negative energy balance of 3500 calories per week, or 500 calories per day.

Why is calorie restriction more important for people with certain genetic backgrounds?

Depending on their genetic background, people react differently to excess dietary calories. For example, those carrying certain variants of the PPAR genes, the ADIPOQ gene, and the LPL gene are more prone to weight gain in response to excess calorie. These variants, ranging in frequency from 25% to 75% in human population, belong to the “thrift genes” that developed to deal with food shortage during human evolution. Carriers of these variants are not able to handle the food abundance in modern society well making calorie restriction more important as a dietary regiment. In addition, genetic variants in the FTO and MC4R genes, appearing in 36% and 22% of the human population respectively, reduce carriers’ satiety.  People with these genetic variants tend to eat in excess without feeling the fullness that signals non-carriers to stop eating and are more likely to be overweight or obese without calorie restriction.

What are calorie-dense foods?

Calorie-dense foods are those that contain a large amount of calories in relation to their portion size. Among the three major calorie sources (fat, protein and carbohydrate), fats yield the most calories per gram.  Therefore, fat-rich foods are among the most frequently encountered calorie-dense food in daily life. Overconsumption of these foods can easily cause weight gain and should be carefully counted by those trying to manage their weight. The following table lists the top 10 common calorie-dense food sources.

Table 1. Top 10 common calorie-dense food sources.

Foods Calories per 100 gram
Plant and vegetable oils 880
Margarine 530-880
Butter, lard, animal fat 700-800
Nuts, Peanut butter 540-730
Seeds (sunflower, pumpkin) 550-580
Fried bacon 540
Chocolate Bars 400-520
Cheeses 310-520
Granola bars 440-470
Cereals 300-400

What are nutrient-dense foods?

Nutrient-dense foods are the ones with higher number of nutrients per calorie. Nutrients include proteins, fats, carbohydrates, vitamins, minerals and fiber. These nutrients provide the body with building materials and functional molecules (although proteins, fats and carbohydrates also provide calories). Most nutrient-dense foods are energy-sparse vegetables, fruits and whole grains but an energy-dense food could be also nutrient-dense, like in the case of cheeses. Meanwhile, foods that provide calories alone are called empty-calorie foods. Foods containing the most empty-calories are the ones with high levels of added sugar and fats. Table 2 lists some common empty-calorie containing foods.

Table 2. Representative empty-calorie containing foods.

Junk food
Candy Bar
Per 100 g 463
Per Serving 162
Serving Size 1.25 oz (35 g)
Per 100 g 405
Per Serving 405
Serving Size 100 g
Per 100 g 399
Per Serving 399
Serving Size 100 g
Per 100 g 349
Per Serving 349
Serving Size 100 g
Alcoholic beverage
Per 100 g 230
Per Serving 97
Serving Size 1 jigger (1.5 fl oz, 42 g)
Per 100 g 43
Per Serving 153
Serving Size 1 can (356 g)
Sport drinks
Red Bull
Per 100 g 45
Per Serving 166
Serving Size 12 fl oz (368 g)
Coca-cola, regular
Per 100 g 32
Per Serving 117
Serving Size 12 fl oz (368 g)
Per 100 g 26
Per Serving 63
Serving Size 8 fl oz (244 g)
Dairy products
Ice creams
Per 100 g 170-240
Per Serving 170-240
Serving Size 100 g

How do I manage daily calorie intake more efficiently?

Keeping track of how many calories you need and how many calories you are eating through the GB Food Calorie and Nutrition Calculator is the most important aspect of daily calorie management.
In addition to this, increasing your intake of nutrient-dense foods, decreasing energy-dense foods, and avoiding empty-calorie foods are general strategies to manage calorie intake efficiently.

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