How do you calculate your BMI?
BMI =   weight (kg) / Height (m) x Height (m) 
 
Why is it important to know your BMI?

On average, an adult man requires about 2,200 calories a day, while an adult woman needs about 1,800 calories.
age:

Older people need fewer calories to maintain the same weight. This is because their metabolism and activity levels are lower. For this group, getting key nutrients like protein and calcium is more important in order to slow down the loss of lean body mass and bone mass.

As for children and teenagers, counting calories is not advised as they are still growing.
level of activity:

if you work in the office, you may need fewer calories than a salesman who is often on the move. 

1. look at the recommended number of servings for children and teenagers
(Look at their recommended number of servings a day)

2. Know the serving size
Look at the table which would help you  get familiar with serving sizes for each of the food groups. 

Recommended Dietary Allowances for Normal Healthy Persons in Singapore (Children & Adolescents)VitaminVit B12Vit B6Ascorbic AcidFolic AcidUnit | mcg | mg | mg | mcg
Age Group |   |   |   | 
0-6 mths | 0.4 | 0.1 | 35 | 65
7-12 mths | 0.5 | 0.3 | 45 | 80
1-2 years | 0.9 | 0.5 | 35 | 150
3-6 years | 1.1 | 0.6 | 50 | 200
Boys
7-12 years | 1.8 | 1.0 | 70 | 300
13-18 years | 2.4 | 1.4 | 105 | 350
Girls
7-12 years | 1.8 | 1.0 | 65 | 300
13-18 years | 2.2 | 1.2 | 80 | 350 

Weight Gain -  Consistently take in more calories than you use through physical activity

Weight Loss - Losing weight does not mean avoiding food instead , 

Physical activity is essential part of any effective weight loss program .
It helps burn calories and build muscles. 
 
What is the importance of physical activity ?

- Cut calories without feeling hungry by swopping deep-fried dishes and items containing curry and gravy with lean protein, fruit, vegetables, whole grains and broth-based soups. The high fibre and water content will keep you feeling full for a longer time.

 -Control your portions. It may help to use a smaller plate and to share desserts with friends. When eating out, ask for less sugar in your drinks. Instead of sweetened drinks, opt for plain or fruit-infused water.

 -If you are patronising food outlets under the Healthier Dining Programme, you can choose lower-calorie options by looking out for dishes marked with the Healthier Choice Symbol.

 -Integrate more physical activity in your daily routine. For instance, park farther away from the mall or home, and walk the extra distance. Take the stairs and walk to your lunch spot.

RECOMMENDED DIETARY ALLOWANCE FOR CALCIUM Age Groups RDA for Calcium
Infants (0 - 6 months, breast-fed) | 300mg
Infants (0 - 6 months, formula-fed) | 400mg
Infants (7 - less than 12 months) | 400mg
Children (1 - 3 years) | 500mg
Children (4 - 6 years) | 600mg
Children (7 - 9 years) | 700mg
Adolescents (10 - 18 years) | 1,000mg
Adults (19 - 50 years) | 800mg
Adults (51 years and above) | 1,000mg
Breastfeeding / pregnant | 1,000mg

A guideline is to eat more "nutrient-dense" food – that is, food that contains plenty of vitamins and minerals, but relatively fewer calories.

Examples include fruit, vegetables, whole grains, lean protein like fish and healthier fats, such as nuts.

however, some food and drinks may appear healthy, but boast an unexpectedly high amount of calories.This is often due to the high sugar or fat content. A glass of fruit smoothie, for example, packs 325kcal. If you were to drink a glass daily on top of your regular diet, you may gain 9kg to 15kg in a year.

Lastly, nuts and nut-based butter are concentrated sources of calories – a handful of mixed nuts contains about 200kcal. It is wise to eat them in moderation. 

Shows the energy and nutrient values of different types of food 

 Infants and young children  

Age | Male | Female
1 month |  410 |  370
2 months |  480 |  430
3 months |  590 |  540
4 months |  530 |  480
5 months |  570 |  520
6 months |  600 |  560
7 months |  620 |  570
8 months |  650 |  590
9 months |  670 |  620
10 months |  690 |  630
11 months |  680 |  640
12 months |  740 |  640
1 year |  880 |  810
2 years |  1080 |  1000
3 years |  1160 |  1070
4 years |  1310 |  1190
5 years |  1440 |  1320

For fruits, it's better to have them whole rather than as juices so that the best of their nutrients are obtained.

The panel, found on packaged foods, will tell you the caloric content of the food as well as nutritional information such as fat, protein and sugar content.

The caloric information helps you approximate how much to eat to stay within your daily recommended intake while the nutritional information helps you make the healthier choice when choosing food products.

For example, keep a look out for important nutrients such as fibre and protein, and avoid products that are high in sugar and saturated fat.

we can estimate the caloric content with this formula:

1g of protein = 4 calories

-Or use the Healthy 365 app, which comes with a database of food and nutritional information and helps you track your meals. These tools will help to manage your calorie and nutritional intake better. 

Choosing whole-grains over refined grains means you get all the goodness that reduces the risk of developing heart disease and diabetes, while helping with weight management since you’ll feel full for longer.