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Why Your Weight Loss Goal Might Be Dangerous

Are you fed up of seeing New Year New Me campaigns?

Often, they are fuelled by companies who want to sell you something – whether it’s a new vitamin drink, an electric bike, or a course of life coaching.

Body weight is a particularly difficult topic for many of us. If you are overweight (and even if you’re not), around this time of year we’re exposed to pressure to shed the Christmas pounds, detox, or *shudder* ‘slim down for summer’.

So how would you feel if I told you there is convincing evidence that from the age of 65, being overweight is healthier than being lighter?

What is Body Mass Index?

Body mass index (BMI) is a tool used to assess weight. It compares weight with height to place you in one of the following categories: underweight, healthy, overweight or obese.

To calculate your BMI, you can use the free NHS calculator.

According to the World Health Organisation, adult BMI categories are as follows:

BMI Category
Less than 18.5 Underweight
18.5-24.9 Healthy
25-29.9 Overweight
30+ Obese


However, BMI is not always an accurate measure of health. For example:

  • Your weight could be within the healthy range despite being a heavy drinker or smoker, eating an unhealthy diet, or being physically inactive
  • Results can be skewed – a body builder may fall into the obese category because of their muscle mass, despite not being overweight
  • The NHS sets different BMI categories depending on your ethnicity and risk of developing health problems related to BMI, so the WHO definitions above may not be accurate for you

However, BMI is still a common measure used by healthcare professionals to assess weight.

How Heavy is Healthy at 65+ Years?

Jane Winter and colleagues looked at the results of 32 studies that had reported the cause of death for adults aged 65 or over. The studies spanned more than 20 years and included 197,940 older adults, giving the data good reliability.

The researchers found that the highest rates of mortality (death) were found at either end of the BMI spectrum – people who had low (20 or under) or high (37+) BMIs.

At the lower end of the BMI scale, your chance of death starts to rise if your BMI is below 23, and once your BMI is 20 or lower, the rate of mortality is 28% higher.

At the other end, mortality rates appeared to be highest in those with a BMI of more than 37.

The lowest risk of death was found in those with a BMI of 27-27.9, even though this falls firmly within the overweight BMI category.

The research concluded that for those with a BMI of 24 to 33, there is no significant increased risk of death.

The point of all of this is that if you are 65+ years old, the research suggests we need to stop trying to achieve a BMI of 18.5-24.9, and instead aim for around 23-30 to reduce our overall risk of death.

Why Does Being Lighter Increase Mortality?

The risk of being underweight, or at the lower end of ‘healthy’, is likely to be related to a condition called sarcopenia.

Sarcopenia is the gradual loss of muscle mass, strength and function that tends to occur from the age of 60 onwards. Although it is associated with aging, muscle loss begins as early as our 30s.

Loss of muscle is a major cause of unintended weight loss in older age. It is dangerous because it increases our risk of falls, reduces our ability to manage daily tasks like cooking and washing, affects our independence and increases our risk of dying.

Research has shown that people with sarcopenia who are admitted to hospital for an acute illness have a poorer prognosis and increased risk of death.

Your weight might be within the healthy or underweight categories, but this could be because you have unintentionally lost weight due to muscle loss.

It is important to remember that the greater your muscle mass, the lower your risk of death. This research suggests that it is more important to focus on building muscle mass than trying to lose fat.

The good news is we can stop muscle loss, and rebuild muscle, at any age with regular strength training (watch this space for our next article on this).

What Do I Need to Do?

The mortality rate is lower if your BMI is within the healthy range for an older adult (23-30).

Whatever your BMI, having a healthy lifestyle is crucial to your overall wellbeing. This means checking that you:

  • Eat a healthy diet
  • Carefully manage any medical conditions with recommended lifestyle changes or medication
  • Stay physically active
  • Take part in strength training to avoid muscle loss
  • Get enough sleep
  • Manage sources of stress

If you want to lose weight, it is best to do so with the help, support and guidance of a dietitian with experience working with the over 65s. This will put a safety net in place to check it is safe for you to lose weight, encourage healthy protein intake, and prevent muscle loss.

Final Thoughts

After reading this, you may have realised that you don’t need to embrace a new you this year. The ‘old’ you may already be just right, and losing weight could actually be harmful to your health.

Comparing the BMI of older and younger people is not the same, so next time you consider your weight, remember that your ideal weight is unlikely to be the same as it was when you were in your 30s.

About Hannah Rose

Hannah Rose worked as a doctor before becoming a freelance medical copywriter. She is passionate about writing the latest in health to empower individuals to understand and take control of their wellbeing. Contact Hannah here.

Tagged under: Women's Health