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Don’t go on a weight-loss diet if you’re not obese…, Harvard study hints

The above graph shows the weight change after ten years in people who were considered lean (blue bars) or obese (red bars) at the start of the study and underwent extreme weight loss of up to 9.9lbs (4.5kg).  It is split into the method used to lose weight (left-hand column gives labels), and the amount of weight either lost or re-gained over ten years compared to people in the same group who did not try extreme weight loss.  All those in the lean group who tried extreme weight loss gained back more weight than their peers, up to 17lbs (7.7kg) more, the study says.  But in the obese group four of the groups managed to keep more weight off ten years later, at up to four lbs (1.2kg) less
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Going on a dramatic weight-loss diet when you’re not obese could actually harm your health years later, a major study suggests.

People already quite lean who lost 10lbs (4.5kg) were at a higher risk of Type 2 diabetes a decade later compared to their peers who didn’t go on an extreme diet.

They were also more likely to pile on the pounds further down the line, according to the research by Harvard University.

The scientists said their results were ‘surprising’.

But they believed lean people who underwent dramatic weight loss had higher levels of hunger hormones, making them more likely to crave junk food.

Many skinny people attempt to lose fat in hope of achieving the ‘Instagram’-style washboard abs or a more toned physique.

But the team at Harvard is now warning that dramatic weight-loss diets should be used only by those who ‘medically need them’.

Results also showed that lean people who lost their weight by following a fad diet or commercial weight loss program were most likely to get fat later in life.

About 40 percent of American adults are overweight, but a previous study found as many as half of women and 20 percent of men who are lean believe they also fall into this category.

The above graph shows the weight change after ten years in people who were considered lean (blue bars) or obese (red bars) at the start of the study and underwent extreme weight loss of up to 9.9lbs (4.5kg).  It is split into the method used to lose weight (left-hand column gives labels), and the amount of weight either lost or re-gained over ten years compared to people in the same group who did not try extreme weight loss.  All those in the lean group who tried extreme weight loss gained back more weight than their peers, up to 17lbs (7.7kg) more, the study says.  But in the obese group four of the groups managed to keep more weight off ten years later, at up to four lbs (1.2kg) less

The above graph shows the weight change after ten years in people who were considered lean (blue bars) or obese (red bars) at the start of the study and underwent extreme weight loss of up to 9.9lbs (4.5kg). It is split into the method used to lose weight (left-hand column gives labels), and the amount of weight either lost or re-gained over ten years compared to people in the same group who did not try extreme weight loss. All those in the lean group who tried extreme weight loss gained back more weight than their peers, up to 17lbs (7.7kg) more, the study says. But in the obese group four of the groups managed to keep more weight off ten years later, at up to four lbs (1.2kg) less

Many lean people try to cut their weight with the aim of achieving washboard abs and 'Instagram-ready' toned bodies.  But the scientists warned this was bad for their health
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Many lean people try to cut their weight with the aim of achieving washboard abs and ‘Instagram-ready’ toned bodies. But the scientists warned this was bad for their health

In what is believed to be the first study of its kind, experts looked at data for 200,000 healthy Americans collected between 1988 and 2017.

Nine in ten participants were female.

They were divided by body mass index (BMI) into those that were lean — had a healthy or underweight range — overweight, or obese.

HOW TO CALCULATE YOUR BODY MASS INDEX – AND WHAT IT MEANS

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

Standard Form:

  • 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 – 39.9: Obese
  • 40+: Morbidly obese

Each was then split into two groups — those who lost 9.9 pounds (lbs) (or 4.5 kilograms, kg) — within a four-year time frame and those who did not.

Weight-watchers were also asked how they lost weight and split into seven groups — a low-calorie diet; exercise; low-calorie diet plus exercise; fasting; commercial weight loss program; diet pills and a combination of fasting, commercial and diet pills.

Scientists then looked at participants’ medical records for another 10 years, on average.

Among lean people, those who went on an extreme diet gained between 4.4 and 17 more pounds (2 to 7.7kg) than their peers.

But among obese people, those who did four of the programs — low calorie diet, exercise, low calorie diet and exercise and fasting — lost between 3.5 and 1.3 more pounds (1.2 to 0.5kgs) than their peers.

The scientists also looked at the diabetes risk for participants.

Lean people who went through dramatic weight loss were up to 54 per cent more likely to get type 2 diabetes than their peers.

But obese adults who went on a strict weight-loss program at some point in their life were less likely to develop diabetes than their peers.

Dr Qi Sun, a Harvard epidemiologist who led the study, said: ‘We were a bit surprised when we first saw the positive associations of weight loss attempts with faster weight gain and higher type 2 diabetes risk among lean individuals.

‘However, we now know that such observations are supported by biology that unfortunately entails adverse health outcomes when lean individuals try to lose weight intentionally.

‘The good news is that individuals with obesity will clearly benefit from losing a few pounds, and the health benefits last even when the weight loss is temporary.’

He said that weight loss likely led to biological changes in lean people that put them at higher risk of piling on the pounds later.

It may raise the levels of hunger hormone ghrelin, leading to someone being hungry more often.

This can also make people more likely to reach for salty or sugary foods because it activates the region of the brain associated with rewards.

Similarly, the researchers warned more fat cells — which release ghrelin — may accumulate in lean people in order to boost levels of the hormone.

At the same time, rapid weight loss ia though to lead to lower levels of anordemandic hormones — like leptin — that help suppress hunger.

Studies also suggest being very lean causes people to move less as a way to conserve energy – making it harder to burn calories.

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