Change4Health - 1. Calories and Energy

Energy is required by all living creatures to support their lives. In common with all other animals, humans take in energy (measured in calories or joules; 1 kcal = 4.2 kJ) released from food and beverages to provide fuel for bodily functions and various physical activities.

Sources

Dietary energy mainly comes from carbohydrates, proteins and fats in foods and beverages. After digestion, they provide different amount of energy to our body.

Energy density values of different nutrients (kcal/gram)
Carbohydrates	Protein	Fat
Each g of carbohydrates provides 4 kcal	Each g of protein provides 4 kcal	Each g of fat provides 9 kcal

Energy Requirement

Daily energy requirement of a person is the amount of energy intake required per day to balance the energy used to maintain his/her daily activities, bodily functions and growth. It varies according to the person’s sex, age, weight, height, health status, as well as level of physical activity. For example, a breastfeeding infant weighing 8 kilograms (kg) requires about 720 kcal a day for optimal growth; a highly active 30-year-old lactating mother may need to take in about 2 900 kcal from foods and beverages a day; while a healthy 60-year-old man with a low level of physical activity may require about 2 100 kcal a day to maintain energy balance.

If you take in more energy than you use to maintain daily activities, bodily functions and growth, you will gain weight (mainly as body fat), leading to overweight and obesity in the long term. Conversely, you will lose weight when you take in less energy than you use. To maintain a healthy weight, you need to balance your energy intake and output - that is, energy intake from food and beverages should be equal to the energy you use.

The Chinese Nutrition Society has estimated the daily energy requirements for the average-built Chinese as shown in the following table.

Estimated daily energy requirement (kcal/day) for healthy individuals with no chronic disease and specific nutritional requirement
Age (year)	Male (kcal/day)			Female (kcal/day)
	Level of physical activity			Level of physical activity
	Light	Moderate	High	Light	Moderate	High
0 -	90 kcal/kg/day			90 kcal/kg/day
0.5 -	80 kcal/kg/day			80 kcal/kg/day
1 -	900			800
2 -	1100			1000
3 -	1 250			1 200
4 -	1 300			1 250
5 -	1 400			1 300
6 -	1 400	1 600	1 800	1 250	1 450	1 650
7 -	1 500	1 700	1 900	1 350	1 550	1 750
8 -	1 650	1 850	2 100	1 450	1 700	1 900
9 -	1 750	2 000	2 250	1 550	1 800	2 000
10 -	1 800	2 050	2 300	1 650	1 900	2 150
11 - 13	2 050	2 350	2 600	1 800	2 050	2 300
14 - 17	2 500	2 850	3 200	2 000	2 300	2 550
18 - 49	2 250	2 600	3 000	1 800	2 100	2 400
Pregnant women
- 1st trimester		-			+ 0
- 2nd trimester		-			+ 300
- 3rd trimester		-			+ 450
Lactating mothers		-			+ 500
50 - 64	2 100	2 450	2 800	1 750	2 050	2 350
65 - 79	2 050	2 350	-	1 700	1 950	-
80 and above	1 900	2 200	-	1 500	1 750	-

Source: Chinese DRIs 2013. Chinese Nutrition Society.

Health Alert

Being obese may shorten life expectancy and increase the risk of various chronic diseases, including type 2 diabetes, coronary heart disease, hypertension, certain cancers such as colon cancer and breast cancer (in post-menopausal women), gallbladder disease and osteoarthritis (knees). However, underweight due to long-term inadequate energy intake may increase the risk of anemia, heart beat irregularities, osteoporosis and bone fracture.

Practical Tips for Eating Well for Fewer Calories

To maintain an optimal weight, it is important to control your energy intake by ‘eating well’. Eating well is not only about what and how much you eat, but also about when and how you eat. The following are some suggestions for eating well:

What to eat?

replace food that are high in calories with those that are lower in calories. For example, have a bowl of rice vermicelli instead of instant fried noodles, fill the dinner plate with an extra portion of cooked vegetables instead of meat, and have an apple as snack instead of chips or cakes;
use low-fat cooking methods, such as steaming, boiling, broiling, braising, grilling, baking or roasting instead of frying and deep-frying;
drink plain water or Chinese tea. Avoid consuming empty calories from sugar-sweetened coffee, tea, soft drinks or alcoholic beverages (these beverages provide calories without any nutrients);
have a healthy snack, such as fresh fruit, if you feel hungry between meals;

How much to eat?

cut down on portions to limit calorie intake, particularly when consuming calorie-dense food and sugary drinks;

When to eat?

eat three regular meals every day. Avoid skipping meals in order to prevent binge eating while at the same time keep your metabolism efficient.

How to eat?

eat slowly to allow time for the brain to sense fullness in the stomach (usually takes at least 20 minutes or more) and to prevent you from eating too much;
stop eating as soon as you feel full.

Go and review your own eating practices and find out what changes you could make to eat well.

Reference

Chinese DRIs 2013. Chinese Nutrition Society.