Science

Start adulthood at a normal weight and slowly add the pounds, scientists say

If we have to put on weight at all, it’s best to start adulthood at a normal weight and ‘slowly add the pounds’, a new study reveals. 

Researchers from Ohio State University looked at data on two generations of people from Framingham, a city in Massachusetts from the ages of 31 to 80.

People who started adulthood at a normal weight and later became overweight – but never obese – tended to live the longest, they found.

Amazingly, adults who fit this definition lived longer than those adults whose weight was in a normal range throughout their life.  

Rather less surprisingly, those who started adulthood as obese and continued to add weight had the highest mortality rate. 

Worryingly, today’s younger generation are becoming overweight and obese sooner in their lives than their parents and are more likely to have deaths linked to increasing obesity, the study also found. 

A new study from researchers at Ohio State University reveals that those who gradually get overweight live longest – even more than those whose weight was in a normal range throughout their life

While the study authors aren’t advising adults to become overweight – officially defined as having a body mass index (BMI) greater than or equal to 25 – they do suggest that if we have to add the pounds, do it later in life.

This is as long as they don’t go too far and become obese, however – having a BMI greater than or equal to 30. 

WHAT IS BODY MASS INDEX (BMI)? 

Body mass index (BMI) is a measure of body fat based on your weight in relation to your height. 

Standard Formula:

  • BMI = (weight in pounds / (height in inches x height in inches)) x 703

Metric Formula:

  • BMI = (weight in kilograms / (height in meters x height in meters))

Measurements:

  • Under 18.5: Underweight
  • 18.5 – 24.9: Healthy
  • 25 – 29.9: Overweight
  • 30 or greater: Obese 

‘The impact of weight gain on mortality is complex,’ said Hui Zheng, study author at Ohio State University.

‘It depends on both the timing and the magnitude of weight gain and where BMI started. 

‘The main message is that for those who start at a normal weight in early adulthood, gaining a modest amount of weight throughout life and entering the overweight category in later adulthood can actually increase the probability of survival.’  

Researchers had sought to identify life-long BMI trajectories across two related generations and ‘estimate their associated mortality risks and population attributable deaths’.  

This was done by following the medical histories of residents of Framingham and their children for decades. 

The researchers used data on 4,576 people in the original cohort of the Framingham Heart Study (FHR) – a long-term, ongoing cardiovascular cohort study of Framingham residents – and 3,753 of their children. 

FHR started in 1948 and followed its original cohort of participants through 2010, while their children were followed from 1971 to 2014. 

The members of the original cohort had almost all died by the end of the study, meaning the results could uncover how BMI evolves over all of adulthood and provide more accurate estimates than before. 

The mortality impact of weight gain depends on an individual's body mass index (BMI) trajectory, researchers say. Pictured, an obese person (obesity is defined having a BMI greater than or equal to 30)

The mortality impact of weight gain depends on an individual’s body mass index (BMI) trajectory, researchers say. Pictured, an obese person (obesity is defined having a BMI greater than or equal to 30)

Of the 4,576 parents, there were 3,913 deaths, and of the 3,753 offspring, there were 967 deaths. 

In both generations, the researchers looked at data from the ages of 31 to 80 years. 

The main measure was BMI, which is based on a person’s height and weight and is used as a rule of thumb to categorise a person as underweight, normal weight, overweight or obese.

After analysing data on how the participants’ BMI changed over the years, the researchers found that the older generation generally followed one of seven BMI trajectories throughout their lives.

The younger generation had six trajectories – there were not enough people who lost weight through their lives to have a downward weight trajectory as was present in their parents’ generation.

After controlling for a variety of factors that have been found to influence mortality, including smoking, gender, education, marital status and disease, the researchers calculated how each BMI trajectory was related to mortality rates.

In both generations, those who started at normal weight and moved to being overweight later in life – but never obese – were the most likely to survive.

Aerial view of downtown Framingham, Massachusetts, US. Similar results were found in two generations of mostly white participants in the Framingham Heart Study, which followed the medical histories of residents of one city in Massachusetts and their children for decades

Aerial view of downtown Framingham, Massachusetts, US. Similar results were found in two generations of mostly white participants in the Framingham Heart Study, which followed the medical histories of residents of one city in Massachusetts and their children for decades

Those who stayed at normal weight throughout life were the next most likely to survive, followed by those who were overweight but stayed stable and then those who were at the lower level of normal weight. 

In the older generation, those who were overweight and lost weight came next.

The least likely to survive were two trajectories involving those who started as obese and continued to gain weight.

While both generations showed the same basic results, the researchers discovered some worrying trends in the younger cohort.

‘The higher BMI trajectories in the younger generation tend to shift upward at earlier ages relative to their parents,’ Zheng said.

The proportion of the sample in higher BMI trajectories systematically increased from the parental generation to their children.

Medical advances mean that people are more likely to survive with obesity now than in the past, but there’s an obesity problem for the younger generation.

‘Even though the mortality risks associated with obesity trajectories have decreased across the generations, their contributions to population deaths increased from 5.4 per cent in the original cohort to 6.4 per cent in the offspring cohort,’ Zheng said.

‘That’s because more people are in the obesity trajectories in the offspring cohort.’

This study, which has been published in the journal Annals of Epidemiology, supports and extends findings from Zheng’s 2013 study American Journal of Epidemiology.

Then, Zheng and colleagues had found that people who were slightly overweight in their 50s but kept their weight relatively stable were the most likely to survive over the next 19 years.

‘Now, with this study, we know more about weight trends earlier in life and how they are related to mortality,’ Zheng said.

As well as being specific to a single US city, researchers said the data was of ‘mostly white participants’, which means there could have been bias in the results. 

OBESITY: ADULTS WITH A BMI OVER 30 ARE SEEN AS OBESE

Obesity is defined as an adult having a BMI of 30 or over.

A healthy person’s BMI – calculated by dividing weight in kg by height in metres, and the answer by the height again – is between 18.5 and 24.9. 

Among children, obesity is defined as being in the 95th percentile.

Percentiles compare youngsters to others their same age. 

For example, if a three-month-old is in the 40th percentile for weight, that means that 40 per cent of three-month-olds weigh the same or less than that baby.

Around 58 per cent of women and 68 per cent of men in the UK are overweight or obese. 

The condition costs the NHS around £6.1billion, out of its approximate £124.7 billion budget, every year.

This is due to obesity increasing a person’s risk of a number of life-threatening conditions.

Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations.

Research suggests that at least one in six hospital beds in the UK are taken up by a diabetes patient.

Obesity also raises the risk of heart disease, which kills 315,000 people every year in the UK – making it the number one cause of death.

Carrying dangerous amounts of weight has also been linked to 12 different cancers. 

This includes breast, which affects one in eight women at some point in their lives.

Among children, research suggests that 70 per cent of obese youngsters have high blood pressure or raised cholesterol, which puts them at risk of heart disease.

Obese children are also significantly more likely to become obese adults. 

And if children are overweight, their obesity in adulthood is often more severe.  

As many as one in five children start school in the UK being overweight or obese, which rises to one in three by the time they turn 10.  


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