Why diets backfire: A year or more after weight loss, the desire to eat grows stronger
One and two years after severely obese people lost about 10% of their body weight, they felt more hungry in general and less full after a meal, a new study finds.
By Melissa HealyStaff Writer
Losing weight is, for most people, the easy part. The bigger challenge is trying to keep it off for more than a year.
New research helps explain why people in this second stage are so much more prone to failure.
In a nutshell, people who have shed a significant chunk of their weight are hungrier and have a stronger desire to eat for at least a year after transitioning from weight loss to weight-loss maintenance. And even when their hormones send loud satiety signals to the brain after a meal, they still don't feel full.
The new study, published Thursday in the American Journal of Physiology-Endocrinology and Metabolism, falls in line with a growing field of research that explores the body's tenacious and multi-pronged response to weight loss.
In a bid to ensure that lost weight is regained, the human body has been found to reset its thermostat to burn fuel more efficiently, to economize in calorie-burning movements and to rev up the impulse to find and eat food.
Researchers believe these responses evolved to protect humans against wasting away during times of famine. But in societies where calorific foods are never in short supply, these adaptations have worked to the detriment of dieters.
Moreover, in people who have become obese, there's growing suspicion that these responses become harder to override. In recent years, researchers have found evidence that obesity makes the brain more "deaf" to some of the gut's satiety signals, and more keenly attuned to signals of hunger.
The new research offers some validation for that surmise.
To study the effects of weight loss in 35 severely obese subjects, Norwegian researchers helped them lose close to a tenth of their weight. They provided dietary advice, exercise coaching and psychotherapy during several three-week stays at a wooded retreat in eastern Norway. All the subjects had a body-mass index greater than 42 (a BMI over 30 is considered obese) at the outset of the study.
At one year, when subjects had lost an average of close to 24 pounds, they returned to the retreat to map out maintenance plans.
Every six months from enrollment to two years out, researchers checked in to conduct a series of tests. Before and for three hours after meals, they gauged subjects' subjective feelings of hunger, fullness and desire to eat, and asked how much food they planned to consume. And they measured circulating levels of five separate hormones that regulate appetite to see how they responded to the prospect of a meal or a meal just eaten.
What they found was the body's reaction to weight loss shifted over time.
In the short run — four weeks after their exercise-and-weight-loss regimens got underway — the subjects had lost an average of 3.5% of their body weight. Their levels of appetite-boosting hormones had risen rapidly — probably a response to their getting roughly 3½ hours of exercise per day while at the retreat.
But they did not report increased hunger or desire to eat. And with rising levels of satiety hormones, they were feeling more full in the wake of eating a meal.
As they met their weight-loss goals, however, things changed.
At the end of a year of dieting and exercise, the study's participants had lost about 7.4% of their weight and had improved their fitness considerably. But they reported to researchers a significant increase in their hunger and desire to eat. And the sensations of fullness they reported after meals had plummeted.
Two years after enrolling in the study — and a year into their weight-maintenance programs — the subjects had, on average, kept the weight from coming back. But they continued to report levels of hunger and desire to eat that were just as high or higher than at the end of Year One. And they reported feeling no more full after a meal.
At both time points, their hormone levels continued to show increases in appetite-stimulating compounds, as well as those that would signal fullness. Though they lost the weight and — with the study's unusual level of support — managed to keep it off, they were hearing the loud cries of their hunger-boosting hormones. The fullness ones, not so much.
The good news, according the researchers: A sustained and supportive program of dietary restriction and physical activity does induce weight loss and can help very obese patients keep the weight off.
The bad news: "Patients with severe obesity who have lost significant amounts of weight … will have to deal with increased hunger in the long-term."
If these patients are to beat the odds and sustain their weight loss, professionals working with them will have to find ways to help them cope with that, they added.
To read this article in Spanish, click here
melissa.healy@latimes.com
@LATMelissaHealy
This is how many pounds you can lose in a year by standing for six hours a day instead of sitting
Polar bears' bodies work 60% harder than thought — which makes surviving climate change even tougher
Galaxies that move together have cosmologists stumped about dark matter
Get our weekly Health and Science newsletter
Melissa Healy
Melissa Healy is a health and science reporter with the Los Angeles Times writing from the Washington, D.C., area. She covers prescription drugs, obesity, nutrition and exercise, and neuroscience, mental health and human behavior. She's been at The Times for more than 30 years, and has covered national security, environment, domestic social policy, Congress and the White House. As a baby boomer, she keenly follows trends in midlife weight gain, memory loss and the health benefits of red wine.
A meteor streaking low across the sky in Puerto Rico has set social media abuzz, with the spectacle amazing some people and unsettling others on an island still being hit daily by small earthquakes.
Court dismisses climate change lawsuit brought by 21 young Americans
A lawsuit by young people who claimed the U.S. government's climate policies jeopardize their future and violate their constitutional rights has been dismissed.
There's more than one way to age. How are you doing it?
Stanford captured a comprehensive view of how we age by profiling 43 healthy adults and taking extensive measurements of their molecular biology over two years.
Turning carbon into concrete could win UCLA team a climate victory — and $7.5 million
A UCLA team is vying for the Carbon XPrize, a competition to see who can recycle the most CO2 by turning it into useful products like concrete.
Microsoft to invest $1 billion in carbon capture with pledge to go carbon-negative by 2030
Latest Science
CTE rears its ugly head again with new Aaron Hernandez documentary
A new Netflix documentary on Aaron Hernandez makes CTE a topic of conversation yet again. The former NFL star was diagnosed with the disease after his death.
A new study suggests that a 'blob' of warm ocean water in 2015 disrupted the food web of the Pacific, triggering the starvation and deaths of thousands and thousands of sea birds, including the common murre.
2019 was the second-warmest year on record, NASA and NOAA say
2019 was the second-warmest year since scientists began taking temperatures in 1880, government scientists from NASA and NOAA announced Wednesday.
This firm spent big to see if 'earthquake lights' could warn of temblors. It didn't work
Stellar Solutions Inc. has mothballed a costly project aimed at improving detection of electromagnetic pulses - 'luminosities' - thought to precede earthquakes.
Researchers create new embryo of nearly extinct rhino species
Only two northern white rhinos remain, and both are female. Their eggs were inseminated in a lab with frozen sperm from dead males, researchers say.