When your BMI is calculated, it will translate to being underweight, in the healthy range, overweight or obese.


If your BMI reading is below 18.5 then you would be classed as underweight and advised to eat more to gain weight within a normal range.

Risks of being underweight

You should consult your GP if you need to gain weight, as low body mass can damage your health and decrease your body’s immune system.

When your immune system is not 100 per cent, you are more likely to catch a cold or other infections, as you lack vital nutrients required for your body to grow, fight infections and work properly.

Among the risks that come with being underweight and having a weakened immune system include:

  • Loss of periods for women
  • Lack of calcium – resulting in failure to maintain strong and healthy bones
  • Malnutrition
  • Weakened muscles – including your heart

Losing weight without trying

If your BMI reading classes you as underweight, and if you have not being trying to lose weight, you should consult your GP to see if other problems are causing this weight loss.

Emotional issues such as feeling anxious when thinking about food could be stopping you from eating a healthy diet.

Experiencing high levels of stress, or other emotional problems, can result in a change in eating patterns that may be hard to recognise, but could result in you losing weight.

If you are exercising control intentionally to avoid eating food, this could be a sign that you may have an eating disorder

Alternatively, there may be an underlying medical cause for your low weight, such as an overactive thyroid

Steps to achieve a normal weight

Adopting a healthy, balanced diet can assist with achieving a normal, healthy weight for your height and age, but it is important to gain weight gradually rather than in a rush. Increasing weight the right way is crucial.

Avoid foods that increase your body fat rather than your lean body mass such as chocolate, cakes and other high-calorie foods.

Aiming for three meals and three snacks a day, involving starchy carbohydrates – such as pasta, rice or potatoes – as well as fruit and vegetables are good healthy eating principles to base your diet on to achieve a healthy weight.

BMI outcomes in adults – Healthy BMI

Having a BMI reading of between 18.5 and 24.9 means you are of a normal weight and that your body is not at risk of a weight-related disease.

It is important to ensure that you maintain your healthy weight through a balanced diet of vegetables, fresh fruit and limited intake of processed food.

If your calorie intake matches your energy output you will remain a normal weight, but exercise is also important, with 30 minutes a day for five days a week recommended for all adults.

Keeping an eye on your waistline can also help monitor any excess weight that might put you at risk of developing long term health conditions.

BMI outcomes in adults: Overweight or obese

If you have a BMI reading of over 25 then you would be classed as overweight, while a reading of 30 or above would see you measured as obese.

Being classed in these groups puts individuals at greater risk of potential risks and illnesses. Doctors may advise you to consult with a bariatric surgeon if your BMI falls in the obese category to help you instigate a weight loss regime.
Among the diseases and health problems that can be more likely to affect overweight or obese people include:

Steps to achieving a healthy weight

Fitness specialists will recommend programs designed to reduce your BMI if you fall into one of these groups.
They will also provide guidance and support over how to change your eating habits and exercise regime to efficiently achieve the best results possible.

Weight loss can improve your health and improve physical ailments such as back and joint pain upon shedding excess weight.


Even losing a small amount of weight can benefit adults who are overweight or obese, and commencing with an excise regime can help you become a healthier weight.

Adults are recommended to engage in at least 150 minutes of physical activity a week, but adults who are overweight will likely need to exercise more than this to lose weight. This could be achieved through cycling , running, swimming


Eating fewer calories by swapping high-calorie meals and snacks for healthier options is an additional part of losing weight.
Swapping energy intake from fats and sugars for increased consumption of fruits, vegetables and whole grains will also assist with weight loss.

Follow-up appointments will often be recommended if your BMI reading is over 25 to ensure that your weight loss goals are being met.

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