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Body mass increase?

Study finds that seniors aged over 65 may lower morbidity risk by carrying a few more kilos.

People aged over 65 who are overweight may live longer, according to new research.

A study from Deakin University found older people with a body mass index (BMI) in the overweight range had the lowest risk of mortality amongst test subjects.

Authors Caryl Nowson, professor of nutrition and ageing, and PhD student Jane Winter, are both dietitians and noticed in practice that those clients carrying a bit of extra weight seemed to do better and enjoy life more by not restricting their food intake.

“We continue to be concerned about older people who restrict their food intake and are likely to be missing out on the nutrients they need,” Nowson said, adding this includes those in residential aged care who are placed on weight reduction diets. She said this is not appropriate.

“Putting too much emphasis on dietary restrictions also increases the risk of malnutrition in this age group,” she explained. “Malnutrition in older people is not well recognised, as this can occur even when BMI is in the overweight range.”

The aim of the study was to determine all-cause mortality risk associated with BMI in those aged 65 and over.

Nearly 200,000 individuals were analysed, with an average follow-up of 12 years. Mortality risk for a BMI of 22–23 was 6 per cent higher than for the reference range (23–24) and the risk continued to increase as BMI decreased. For example, the increase in mortality risk from the reference range was 19 per cent for those with BMI of 20–21.

Above the reference range, mortality risk did not increase significantly for BMI between 24 and 33; then it began to rise, starting with an 8 per cent increase for BMI above 33.

A BMI of 27, which is around the middle of what is considered to be the overweight range, encountered the lowest risk.

“Older people in the overweight range do not need to restrict their food intake, and dieting to lose weight is not necessary,” Nowson said. “It is important to monitor the BMI of older people … and to be alert to any problems if their BMI falls below 23.”

Nowson said the current BMI recommended range is not suitable for those over the age of 65.

“A number of organisations allude to this, but there has not until this study been any strong evidence base to back up the recommendation,” she said. “We no longer have specific dietary guidelines for older people and many professionals do not recognise that the dietary guidelines are not relevant to older, frailer adults.

“Rather than focusing on weight loss, older people should put their efforts into having a balanced diet, eating when hungry and keeping active, Nowson said.

Whilst she explained that the findings do not change the message to the adult population outside of this age group – that maintaining a healthy weight and being physically active is important in reducing mortality and chronic disease – for those aged 65 and over there is “no evidence that trying to achieve a BMI less than 25 reduces mortality and, in fact, the evidence shows there is more risk associated with lower BMIs”.

However, Dr Grace Joshy, research fellow at Australian National University’s National Centre for Epidemiology and Population Health, said a good overall prognosis is associated with maintaining a normal weight over the course of life.

“There is clear evidence that the risks of cardiovascular disease and cancer are higher for those who are overweight or obese,” Joshy said. “Those who survive to older age despite being constantly overweight have a higher risk of death and of mobility-related disability, compared with those who maintain a normal weight.”

She added those with lower BMIs are a mix of smokers, people who have lost weight due to an underlying disease, and those who have maintained a lean weight due to a balance of physical activity and caloric intake.

“Without individual participant level data, careful adjustments for pre-existing illnesses and smoking habits are not possible,” she said.

Aloysa Hourigan, senior nutritionist and nutrition program manager at Nutrition Australia, said provided the findings and the use of the recommendations are kept in context, changing the higher limits for those aged over 65 could be beneficial.

“It is important to base guidelines for healthy weight around evidence,” Hourigan said. “This evidence identifies there may well be a need to reconsider the advice for the healthy weight range BMI for people over the age of 65 years.

“There has been previous research that supports a best practice guideline of aiming for a BMI of 22–27 for older persons (over 70 years) and that supports the finding of the Deakin study. This is the advice dietitians would give to older persons.”

Hourigan added, however, that it should not be at the expense of sound management of chronic diseases. She said the suggestion for higher limits for the healthy BMI range for over 65s should be considered carefully; advice would need to be given based on an individual’s issues – something Nowson agreed with.

Hourigan said, “If chronic disease management – for example glycemic control in type 2 diabetes, or mobility levels for those with arthritis or joint problems – would be improved by a person reducing their level of body fat or weight, then this may also influence what is seen as the healthy BMI for an individual person.

“These findings will have to be considered along with other research in this area before changes to recommendations are made but this is a significant piece of research that does suggest a change to recommendations may well be warranted.

“It would be support from bodies such as the NHMRC that would be integral to moving forwards with any change in the recommendations.

“For older persons, where it is advised that some weight loss would be beneficial for management of other health issues, any recommended strategies should emphasise maintaining an adequate nutrient intake and aiming for gradual, not rapid, weight loss –with some physical activity to help protect lean body mass.”

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