ostdoctoral research fellow, Epidemiology, University of Cambridge explains how type two diabetes weight loss recommendations could be harmful for some.
People with type two diabetes are often encouraged to lose weight, as this can help return their blood sugar to normal levels.
But few studies have actually looked at how weight loss affects these patients’ long-term health, including their risk of heart disease (the most common diabetes complication and the leading cause of death) and risk of premature death. This is what our latest study sought to investigate.
Our results showed that large weight loss (more than 10% of body weight) during the five-year period after type 2 diabetes diagnosis was associated with a two-fold increased risk of premature death from any cause.
The risk of death after weight loss was highest among participants who did not have obesity at the time they were diagnosed, suggesting obesity could be a particular factor in how patients are affected by losing weight.
Our study included 2,730 adults with a new diagnosis of type 2 diabetes from the UK, Denmark, and the Netherlands. Their ages ranged from 40 to 69, and 42% were women.
Our aim was to understand whether weight loss after a diabetes diagnosis was associated with risk of heart disease and mortality, and whether short- and long-term weight loss had different effects.
We first measured participants’ weight at the time of their diabetes diagnosis, then again one year and five years later. Then, for the next five years, we tracked information on participants’ heart disease diagnoses and deaths from hospital records and national registries.
Patients who gained weight in the year after diagnosis were three times more likely to die by the end of the 10 year study than those who maintained their weight. Losing weight and then regaining was also associated with double the risk of death.
Over the five-year period, steady, moderate weight loss showed no effect on heart disease or mortality. And large weight loss led to no increased risk of death among people who had obesity.
But those who did not have obesity and lost more than 10% of their body weight had more than three times the risk of death than someone who maintained their weight.
We didn’t find any associations between weight changes and risk of heart disease across any of the time periods we studied.
Our study is one of the first to show that weight loss may have different effects on different diabetes patients, depending on their body mass index (BMI).
Other studies have shown that large amounts of weight loss among people with diabetes may increase risk of death. However, these findings were often attributed to unintentional weight loss, or weight loss due to being unwell.
The participants in our study were given an information booklet on healthy diet and exercise habits, but they were not given any specialised support to lose weight.
While people with a recent diagnosis of type 2 diabetes are often motivated to make healthy lifestyle changes, it’s possible that the weight loss seen in our study’s participants was unintentional.
However, we used information on age and participants’ self-rated health to see whether these factors might have affected the results from our study.
We did not see any evidence of bias from unintentional weight loss due to older age or poor health, so we don’t think that unintentional weight loss entirely explains our results.
Why is weight loss a risk?
It’s unknown why weight loss would increase risk of death. It’s possible that other factors besides BMI are important, such as diabetes severity or having other chronic health conditions like cancer, as these all affect a person’s risk of death.
We also checked if age was important in how weight loss affected mortality, though there weren’t any differences in the effect of weight loss on mortality for younger or older people.
Someone’s behaviour related to diet and exercise, and whether they have other illnesses, may also affect their mortality risk.
In order to figure out which patients might benefit from weight loss, and which might be harmed, more research should consider these other factors besides BMI.
Although patients with type 2 diabetes receive personalised medical treatment depending on factors such as their blood sugar levels, whether they have other health conditions, and what medications they take, weight loss advice, unfortunately, doesn’t follow a similar approach.
Instead, patients who are overweight are typically advised to reduce their calorie intake, or exercise more, following international guidelines.
Based on our study’s results, it’s possible that advising weight loss to all people with type 2 diabetes may not be the best approach. Instead, weight loss advice for people with type 2 diabetes should also be tailored, to reflect that weight loss may affect patients differently.
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