Being underweight can be the result of an underlying medical condition, an eating disorder, or excessive athletic activity. There are some warning signs that can occur when your body weight becomes too low, including lethargy, anxiety and a loss of muscle bulk. You can also determine if you are underweight by calculating your body mass index (BMI). BMI is the division of your weight (in kilograms) by your height (in meters) squared. For example, if you weigh 80 kg, and your height is 1.78 m, your BMI is 25.25. You are classified as underweight if your BMI is less than 18.5 kg/m2.
Did you know? If your BMI is less than 18.5, your health could potentially benefit from gaining some weight.
It’s thought that being significantly underweight can potentially be detrimental to your health, resulting in decreased immunity and poor disease tolerance. Research has also shown that underweight men face the potential risk of a reduction in bone density.
A 2008 study reported in the American Journal of Epidemiology found that low body weight among middle-aged men was related to their risk of osteoporosis three decades later. Men who gained weight over that time reduced their risk, yet men who lost more weight over the 30 years increased their risk.
According to the researchers, being underweight is a strong and independent risk factor for osteoporosis and hip fracture in men (and women), and should be prevented if possible.
Whether you need to gain weight for medical reasons or to change your body shape to improve your athletic performance, the lifestyle strategies are very similar. It's vital that you eat more kilojoules than your body burns off and follow an eating plan that is virtually the opposite of a weight loss diet. But it's not about eating junk food, or large quantities of eggs and steak. To make sure that the type of weight you gain is muscle and not fat, try to adopt the following strategies.
Eat regularly – Eat breakfast, lunch and dinner, and then aim to eat something mid-morning, mid-afternoon and after dinner. Focus on quality foods including vegetables, oats, pasta, lean meats, eggs, nuts, seeds, dried fruit, yoghurt and bread. Don't let two or three hours go by without eating something. A dietary supplement may also help to ensure you have all the nutrients your body needs.
Eat more than normal – If you want to weigh more than you do now, you have to eat more than you do now. By eating an extra 1000 kilojoules each day (i.e. an extra apple, slice of fruit loaf with jam and a small yogurt), you may gain around 1 kilogram per week.
Drink your meals – Drink juice, sports drinks, skim milk and smoothies to give you added kilojoules without making you feel full. Adding protein powder to your drinks may also help to build muscle mass.
Eat healthy fats – Eat plenty of healthy fats found in nuts, avocados, fish and olives to provide extra kilojoules and nutrients. Go easy on saturated fats from animal products (fatty meats, butter and cheese) which may have a negative effect on your heart health.
Lift weights – Diet alone can cause weight gain, but without weight training, you will tend to gain fat and not muscle. Performing resistance training two or three times per week is ideal.
Eat before bedtime – Eating a late night snack will ensure your body has plenty of fuel when your body repairs and rebuilds itself overnight. Just make sure it is a light meal (i.e. toast, fruit or a smoothie) that doesn't interfere with your sleep.
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