Do I need to gain weight? How do I know if I am underweight? How do I know if I have lost too much weight? And what is my target weight if I am trying to gain weight?
While overweight and obesity often feature heavily on TV and online, and many people you know wish to lose a few pounds – another large group of our society wish to gain weight. And this group of people is rarely talked about in newspapers or on TV. Being underweight or losing weight unintentionally may bring about its own risks. Knowing when its time to take action is hugely important!
Are you underweight or losing weight unintentionally?
What are the risks of being underweight or losing weight without trying to?
- Malnutrition
- Vitamin and mineral deficiencies
- Decreased immune function
- Fertility issues
- Increased risks of complications from surgery
- Growth and development problems in children and teenagers.
Why might I be losing weight?
For some of you, weight loss may happen without trying. You may lose weight from a poor appetite, from being ill, from exercising more than you can eat. For others, you may have never been heavier and were always underweight.
Some potential causes of unexpected weight loss may include (2):
- Depression
- An over-active thyroid (under over-treating an under-active thyroid).
- Cancer
- Side effects of some medications.
- Heart, liver, lung or kidney disease.
- A problem with certain glands that secrete hormones, such as Addisons Disease, or Diabetes.
- Dental problems
- Some inflammatory conditions such as lupus or rheumatoid arthritis.
- Dysphagia (a problem swallowing foods)
- Gut issues such as a stomach ulcer, inflammatory bowel disease or coeliac disease.
- Some people with dementia may be experiencing difficulties with eating.
- A viral, parasite of bacterial infection.
If you are losing weight without trying to, it would be useful to discuss this with your GP and dietitian. Unintentional or unexplained weight loss may be a symptom of some medical conditions. It may also be a side effect of some treatments and medications used to manage conditions.
Why should I try to gain weight?
There are many reasons why people may be trying to gain weight. These may include:
- You may be underweight and wish to gain some weight to feel and look better.
- You are/have been ill and have lost weight. You now hope to gain this weight back to build up your strength.
- Your appetite is poor and you are not able to eat enough to keep up your weight.
- You are an older adult and have lost weight without trying.
- You exercise a lot and wish to build muscle and strength rather than lose weight to help you perform better.
Am I underweight?
We often use BMI (Body Mass Index) to calculate whether someone’s weight may fall into an “underweight” category (1). What you need to measure your BMI is your weight, and your height.
How do I measure my weight?
Check your weight in the morning, when you have an empty stomach and an empty bladder. Stand with your bare feet on the scales, and take your weight in kilos (kg).
How do I measure my height?
Stand against the wall in your bare feet and look straight ahead with your feet close together. Make sure your heels touch the wall. Have a friend hold a ruled onto your head and against the wall and make a small light pencil mark. Use a tape measure to measure your height from the floor to the mark (use meters).
Use the BMI calculator below to calculate your own BMI, or use a calculator to make the following calculation: Weight (in kg) ÷ Height (in meters) ÷ Height (in meters). This is your BMI.
What are the BMI categories?
The following categories are used by the World Health Organisation when classifying BMI.
- Underweight: Less than or equal to 18.5.
- Healthy Weight: between 18.5 and 25.
- Overweight: between 25 and 30.
- Obese: More than 30.
If you are a healthy weight, overweight or obese and have lost weight without trying to, this can still mean you are at risk of malnutrition. We will discuss how to categorise your unintentional weight loss further down in this article.
What is my target healthy weight range?
If you are underweight according to your BMI, we can use our height to calculate our healthy weight range. Use the below calculator to find out your weight range that will meet the “healthy” BMI category for your height. Put in your height and find your healthy weight range.
How much unexplained weight loss can put me at risk of malnutrition?
Unexplained weight loss of about 5% of your body weight over 6-12 months may be a cause for concern. At this rate of weight loss, you may be at risk of malnutrition.
More specifically, some research (3) now reports an increased risk of malnutrition if you have lost:
- 1-2% body weight in 1 week.
- 5% body weight in 1 month.
- 7.5% body weight in 3 months.
- 10% body weight over 6 months.
How much weight should I gain?
A big first step for many people would be to stop losing weight. Aiming for weight maintenance may be a huge first goal to achieve, before looking at possible weight gain.
If you are underweight, a healthy amount of weight to gain is usually ½ to 1kg per week, until you reach your target healthy weight.
For people who are losing weight unintentionally and are in the healthy, overweight or obese BMI categories, a good goal would be to aim for weight maintenance. Building muscle strength back may lead to some weight gain, but other than this, we usually do not focus on rebuilding fat stores when someone is in these weight categories.
Knowing when to seek help:
If you have lost weight recently without trying, it is a good idea to discuss this with your GP (General Practitioner) and Registered Dietitian. If you wish to see a dietitian, speak to your GP or seek a private dietitian through www.INDI.ie.
I have some useful articles on this website for those who are looking to rebuild some weight. You can read my article on the top 5 habits to gain weight by clicking here. And here is an article about 7 practical food choices to make if you are trying to gain weight. For more information about the differences in eating when well or unwell, click here.
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