Underweight Children


Children are still growing, which means they need the energy (calories) and nutrients that come from a varied and balanced diet. If your child is underweight, they may not be getting enough calories.

If you're concerned that your child is underweight or not growing normally, see a GP. Low weight can occur for a number of reasons.

How can I tell if my child is underweight?

As a parent, it can be difficult to tell if your child is underweight. If you already know your child's height and weight, and want to know if they're a healthy weight, you can check using our healthy weight calculator.

If your child is in Year 6 (ages 10 and 11), they may have already been weighed and their height measured as part of the National Child Measurement Programme.

In some areas you may be sent the results for your child. In other areas you will have to contact your local authority to find out your child's measurements.

If results show that your child is underweight, consult a GP, who can talk to you about the possible causes. If there is a problem with your child's diet, the GP can give advice that will help bring your child up to a healthy weight, or refer them to a dietitian.

Your child's diet

All children need the energy (calories) and nutrients that come from a varied and balanced diet. If your child is underweight, it may be tempting to fill them up with high-calorie but unhealthy foods, such as sweets, cake, chocolate and sugary and fatty foods and drinks. However, it's important that your child gains weight in a healthy way, and this means eating a balanced diet.

Once your child is 5, they should be eating a healthy, low-fat diet like the one recommended for adults.

What is a balanced diet?

The government advises that children aged 5 and over follow the Eatwell Guide. This guide shows the proportions in which different types of foods are needed to have a balanced diet: 

  • Eat at least 5 portions of a variety of fruit and vegetables every day.
  • Base meals on potatoes, bread, rice, pasta or other starchy carbohydrates. Choose wholegrain where possible.
  • Have some dairy or dairy alternatives (such as soya drinks and yoghurts). Choose lower-fat and lower-sugar options.
  • Eat some beans and pulses, fish, eggs, meat and other protein. Aim for 2 portions of fish every week – 1 of which should be oily, such as salmon or mackerel.
  • Choose unsaturated oils and spreads and eat in small amounts.
  • Drink plenty of fluids – the government recommends 6 to 8 glasses a day.

Try to choose a variety of different foods from the 5 main food groups. Consume foods and drinks that are high in fat, salt and sugar less often and in small amounts.

Most people in the UK eat and drink too many calories, too much fat, sugar and salt, and not enough fruit, vegetables, oily fish or fibre.

Children's meals at home

Do you find it difficult to make time to prepare healthy balanced meals for the whole family? If so, that might be part of the reason your child is not consuming enough calories.

Try to make time for breakfast and dinner, and eat together as a family. Make mealtime a fun part of the day.

Children's lunches

During the week, your child will eat lunch at school. It's impossible to monitor exactly what your child eats away from home, but you can help your child make healthy choices.

  • Talk to your child about the importance of a healthy and balanced diet.
  • Give your child prepaid school lunches, or a healthy packed lunch, instead of giving money that your child can spend on food.
  • Find out what the school's healthy eating policy is.

These days, school lunches are more likely to meet a child's nutritional requirements compared with the average packed lunch. If you would prefer to make your child a packed lunch, make sure it is nutritionally balanced.

A healthier packed lunch should:

  • be based on starchy carbohydrates (bread, potatoes, rice, pasta)
  • include fresh fruit and vegetables/salad
  • include protein such as beans and pulses, eggs, fish, meat, cheese (or dairy alternative)
  • include a side dish, such as a low-fat and lower-sugar yoghurt (or dairy alternative), tea cake, fruit bread, plain rice/corn cakes, homemade plain popcorn, sugar-free jelly
  • include a drink, such as water, skimmed or semi-skimmed milk, sugar-free or no-added sugar drink

How to increase your child's calorie intake

To help your child gain weight, try increasing their portion sizes at mealtimes, especially for starchy foods such as bread, rice, pasta and potatoes.

Alternatively, if your child finds it hard to eat larger portions, try increasing the energy density of your child's meals, until they have reached a healthy weight.

Energy density is the amount of energy (calories) per gram of food. Higher energy density foods tend to be higher in fat, such as cheese, nuts, whole milk and nut butters.


  • a jacket potato with baked beans topped with grated cheese
  • tuna pasta bake
  • mashed avocado topped with chopped hardboiled egg on wholemeal toast

You can also boost your child's daily calorie intake by providing healthier snacks. Great snack ideas include:

  • small sandwiches with a protein filling, such as cheese or eggs
  • cheese and crackers or cheese on wholemeal or brown bread
  • yoghurt, which contains protein and calcium
  • breadsticks and vegetable dips such as hummus

Keep your child active

Even if your child is underweight, it's still important that they're physically active. Physical activity helps them develop strong, healthy bones and muscles. It's an important part of how they learn about themselves and the world. And, best of all, it's great fun.

Children over 5 should do a minimum of 60 minutes of activity each day. But the amount of physical activity your child should do may be different if they're underweight. A GP, practice nurse or school nurse can advise you on this.

Monitor your child's progress

If you provide a healthy diet using these guidelines, you should see your child's weight and growth improve. Keep regular records of your child's height and weight, and take your child back to the GP to check that their weight gain is happening as it should.

Once your child has reached a healthy weight, their diet may need adjusting so that they do not become overweight.

Helplines & Web Chats

NSPCC - Helpline
Parenting NI Free support line
Family Lives - Forum
ParentLine NI
ParentLine NI
Family Lives Forum