Going on a drastic weight loss diet when you’re not obese could actually hurt your health years later, a large study suggests.
People who were already quite skinny and lost 4.5 kg were at a higher risk of type 2 diabetes ten years later than their peers who did not follow an extreme diet.
They were also more likely to pile on the pounds further down the line, according to the Harvard University research.
The scientists called their results “surprising.”
But they believed that lean people who experienced dramatic weight loss had higher levels of hunger hormones, making them more likely to crave junk food and gain fat more easily.
Many skinny people try to lose fat in hopes of achieving “Instagram”-esque washboard abs or a toned physique.
But the Harvard team now warns that dramatic weight loss should only be used by those who “need them medically.”
The results also showed that lean people who lost their weight by following a fad diet or commercial weight loss program were most likely to become fat later in life.
About 40 percent of American adults are overweight, but a study of University of Massachusetts found as many as half of women and 20 percent of men who are slim believe they also fall into this category.
Scientists at Harvard University followed people for ten years after they lost 4.5 kg. They were broken down by where they were lean (blue bars) or obese (red bars) at the start of the study, and by weight loss (labels on the left). Each group was then compared with other participants in the same category who were not trying to lose weight excessively. The results showed that lean people who did extreme weight loss were likely to be heavier than their peers ten years later, while for obese people it had the opposite effect.
Many lean people try to lose weight with the goal of getting washboard abs and “Instagram-ready” toned bodies. But the scientists warned that this was bad for their health
In what is considered the first study of its kind, experts looked at data from 200,000 healthy Americans collected between 1988 and 2017.
Nine out of ten participants were women.
They were divided by body mass index (BMI) in those who were lean — healthy or underweight — overweight or obese.
A healthy BMI means that a person is likely to have a good body fat to height ratio, putting them at no risk for obesity-related diseases such as high blood pressure.
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.
- BMI = (weight in pounds / (height in inches x height in inches)) x 703
- BMI = (weight in kilograms / (height in meters x height in meters))
- Under 18.5: underweight
- 18.5 – 24.9: Healthy
- 25 – 29.9: overweight
- 30 – 39.9: obese
- 40+: Morbid obesity
Each was then split into two groups — those who lost 9.9 pounds (lbs) (or 4.5 kilograms, kg) — within the span of four years and those who didn’t.
Weight Watchers was also asked to say how they lost weight and divided into seven groups – a low-calorie diet; excercise; low-calorie diet plus exercise; fasting; commercial weight loss program; diet pills and a combination of fasting, commercial and diet pills (FCP).
Scientists then monitored the participants’ medical records for an additional 10 years on average.
Among lean people, those on an extreme diet gained between 4.4 and 17 pounds (2 to 7.7 kg) than their peers.
But among obese people, those who took four of the programs — low-calorie diet, exercise, low-calorie diet, and exercise and fasting — remained between 3.5 and 1.3 pounds (1.2 to 0.5 kg) more than their peers.
In the three others – commercial weight loss plan, pill and FCP – obese people did not gain more than 2.8 kg compared to their peers.
In lean people, none of the plans led to more weight loss ten years later than if they had done nothing.
This was the same for the overweight group, where they gained up to 7 kg more than their peers.
The scientists also looked at the diabetes risk for participants.
Skinny people who experienced dramatic weight loss were up to 54 percent more likely to develop type 2 diabetes than their peers.
But all the obese adults who did the plans were less likely to develop diabetes than their peers.
The scientists did not calculate average numbers between those who did different weight loss plans but fell into the weight category.
Overweight adults who lost weight quickly were up to 42 percent more likely to develop diabetes than their peers.
dr. Qi Sun, a Harvard epidemiologist who led the study, said: “We were a little surprised when we first saw the positive associations of weight loss attempts with faster weight gain and a higher risk of type 2 diabetes in lean individuals.
“However, we now know that such observations are supported by the biology that unfortunately carries with it adverse health outcomes when lean individuals deliberately attempt to lose weight.”
“The good news is that obese people clearly benefit from losing a few pounds, and the health benefits persist even if the weight loss is temporary.”
He said weight loss likely led to biological changes in lean people that put them at greater risk of piling on the pounds later on.
It can increase levels of the hunger hormone ghrelin, making a person feel hungry more often.
This can also make people more likely to reach for salty or sugary foods, as it activates the area of the brain associated with rewards.
Likewise, the researchers cautioned that more fat cells — which release ghrelin — may build up in lean people to increase levels of this hormone.
At the same time, rapid weight loss led to lower levels of anorexigenic hormones — such as leptin — that help suppress hunger.
Studies also suggest that it causes the body to reduce the amount of energy it burns, to ensure that more energy is conserved.