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What does ‘Weight for Height’ and ‘BMI’ mean?
You continue growing in height until the age of 18 - 20 years old. It is important that you also continue to put the correct amount of weight on during this time, so that your body develops strong muscles and bones.
Everyone should be at an optimum weight for their height at a certain age. Ideally this should be 100% to be healthy - 85% weight for height is safe but not healthy and is classified as malnourished.
BMI stands for ‘Body Mass Index’. A healthy adult will have a BMI of between 20 -25kg/m2. BMI varies depending on the age of a young person, but by the time you are 17 or 18 years old your BMI should be within the adult range.
Weight (kg) = BMI (kg/m2)
Height (m)2
I feel full of energy and well now, why do I need to gain weight?
Your body adapts temporarily to being underweight but continued
starvation will eventually lead to tiredness and fatigue. Cutting down on calories means you also cut down on essential minerals such as iron, calcium and vitamins which can cause serious health problems such as anaemia.
Anorexia can affect your body’s ability to grow in height. Remember, restoring your weight is an important part of becoming healthier, it will help you gain height and strength too.
Should I wake my son/daughter if they are sleeping at a meal or snack time?
Yes - regular meal and snack times are essential. The body needs regular fuel from food to sustain itself and if meals or snacks are missed the desire to continue fasting increases. To help maintain a regular meal pattern, meals and snack times may be seen as medication.
It is difficult to organise our day around the eating plan. Any suggestions?
Within family life there will be conflicting schedules with work, school and other activities. It is a demanding and exhausting time, but it is essential to plan each day. It may help to spend 30 minutes on a Sunday planning meal for the week ahead, or if a week is too long, then just do two days at a time.
Having other family members eat together means that your son or daughter knows everyone is trying to help him or her. Setting time limits for meals and snacks may also help.
When I start to eat, I feel full straight away
This is normal. When you haven’t eaten properly for a while your stomach shrinks and the rate at which it empties slows as well, meaning you may feel full for longer even if you have only eaten a very small amount of food.
You may also experience stomach cramps and for this reason, you may be advised to eat quarter or half portions from your meal plan to start with until your stomach starts to return to a normal size.
The feeling of fullness and cramps will lessen as you start to eat
more regularly.
When I start to put on weight, it all goes onto my stomach. Why?
Underweight people have concave abdomens. A person of healthy weight has a convex abdomen. Loss of muscle tone can lead to the belief that you are gaining weight/fat just in this area. Temporarily after a meal the stomach will need to expand a little but after a few hours the food is broken down and used throughout the body, returning the abdomen to its previous shape. As you have experienced an empty tummy for a period it will seem unfamiliar to have a full one.
Initially when you gain weight it may be stored near your stomach as this is where it is most easily turned back into energy if you do not eat enough. If you manage to maintain the weight gain the fat around your middle will be re-distributed around your body and used for muscles, healthy skin etc.
Why is milk so important to my diet?
Milk contains protein and calcium, both of which are important to build strong muscles and bones as well as other essential nutrients. You have probably been advised to take full cream milk to help boost energy intake.
Liquids may be easier for you take when you first start on your eating plan e.g. milkshakes (shop brought or homemade). Other good sources of these nutrients are cheese, fromage frais and yoghurt - try grating cheese if you cannot take it in one piece.
Do I need extra food for exercise?
Yes - extra energy needs to be provided to allow you to exercise efficiently. For every twenty-five minutes of exercise have an extra snack from List B on your meal plan.
Feeling fat?
If you cannot escape ‘feeling fat’ talk to one of the eating disorders team. Fat is not a feeling. You may be feeling unhappy, stressed or frustrated.
Will I exceed a healthy weight?
In time, your body will adjust to accepting food again. As you get nearer a normal weight you will learn to recognise feelings of hunger. This will give you confidence to know that you will not lose control. Staff will help to monitor correct weight gain by gradually altering the content of your meals and snacks.
By eating at regular intervals, you should never get too hungry and this will reduce the risk of overeating.
Even though I have started eating a bit more I am still constipated?
Constipation is a common problem as low weight and irregular eating causes sluggish bowels. Regular eating and adequate fluids will help to ease constipation over time. If you are worried, one of the staff will listen to your bowel and can reassure you.
I feel tired and cold. What can I do?
Loss of weight means not only loss of the fat which insulates and protects our body but also affects our muscles including the heart which helps to maintain our body temperature by pumping warm blood around the circulation.
You may have noticed other physical changes such as your skin becoming dry or your hair becoming thin. There can sometimes be some growth of fine body hair on the face and neck. Anaemia (lack of iron in the blood) causes tiredness.
All these changes are a normal response to starvation BUT they can be reversed by eating a healthy diet. The sooner normal eating is resumed, the quicker these physical changes will resolve.
I am worried because Christmas is near. What can I do?
If you are recovering from an eating disorder, Christmas, Easter and other family occasions can be a very stressful time. Keep to your meal plan, maintain the same structure as your usual daily eating pattern.
Do not allow more than a four-hour gap between eating.
Plan what you are going to eat before the day and discuss your plan with a member of staff and your parents.
Parents should remind their child if necessary that it is time for a meal or snack but try not to persuade them to eat more than is on the meal plan.
We are going on a family holiday soon. Should we do anything different?
As for Christmas and other occasions, structure and meal planning are important. Again, keep to the meal plan and treat meal and snack times as ‘medication’ if this helps.
Keep an eye on the time, allowing a maximum of four hours between eating, except for overnight.
Ensure a bedtime snack is included to prevent hunger during the night.
Can I use Quorn in my diet?
We suggest you use Quorn as a protein substitute for a main meal up to a maximum of three times a week. Quorn does not contain essential minerals such as iron and zinc.
I never feel hungry
When you have eaten less food than you need for a length of time your body will take a few months to recognise what it is like to feel hungry. This can make it very difficult to start to eat but is important that you do - take it one meal at a time.
When feelings of hunger return this can often make you feel anxious as you are coping with hunger which you have previously been denying. Talk to a member of staff who will help you understand why you may be feeling this way.
Do I need to take any dietary supplements?
Extra nutrients may initially be advised by the team if a blood test shows deficiency. The meal plans have been devised to meet all nutritional requirements so long term dietary supplements will not be necessary.
BEAT (Beating Eating Disorders)
Unit 1 Chalk Hill House
19 Rosary Road
Norwich
Norfolk
NR1 1SZ
help@beateatingdisorders.org.uk
BEAT Helpline – 0808 801 0677 (help
help@beateatingdisorders.org.uk
BEAT Youthline – 0808 801 0711 (12pm-8pm, 4pm-8pm bank holiday and weekends)
Contact us
If you have any queries relating to this information, please contact the Dietetics service.
About this information
Service:
Dietetics
Reference:
DT/091
Approval date:
22 May 2026
Review date:
1 May 2029
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Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.