NEW YORK (AP) _ Any dieter knows that it's hard to keep off weight you've lost. Now a study finds that even a year after dieters shed a good chunk of weight quickly, their hormones were still insisting, “Eat! Eat! Eat!”
The findings suggest that dieters who have regained weight are not just slipping back into old habits, but are struggling against a persistent biological urge.
“People who regain weight should not be harsh on themselves, as eating is our most basic instinct,” Joseph Proietto of the University of Melbourne in Australia, an author of the study, said in an email. The research appears in Thursday's issue of the New England Journal of Medicine.
Weight regain is a common problem for dieters. To study what drives it, Proietto and his colleagues enrolled 50 overweight or obese patients in a 10-week diet program in Australia. They wanted to see what would happen in people who lost at least 10 percent of their body weight. Ultimately, only 34 people lost that much and stuck with the study long enough for analysis.
The program was intense. On average, the participants lost almost 30 pounds (13.6 kilograms) during the 10 weeks, faster than the standard advice of losing 1 or 2 pounds (0.45 to 0.91 kilograms) a week. They took in 500 to 550 calories a day, using a meal replacement called Optifast plus vegetables for eight weeks. Then for two weeks they were gradually reintroduced to ordinary foods.
Despite counseling and written advice about how to maintain their new weights, they gained an average of 12 pounds (5.4 kilograms) back over the next year. So they were still at lower weights than when they started.
The scientists checked the blood levels of nine hormones that influence appetite. The key finding came from comparing the hormone levels from before the weight-loss program to one year after it was over. Six hormones were still out of whack in a direction that would boost hunger.
The dieters also rated themselves as feeling hungrier after meals at the one-year mark, compared to what they reported before the diet program began.
Experts not connected to the study said the persistent effect on hormone levels was not surprising, and that it probably had nothing to do with the speed of the weight loss.
People who lose less than 10 percent of body weight would probably show the same thing, though to a lesser degree, said Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge, Louisiana.
A key message of the study is that “it's better not to gain weight than to try to lose it,” Bray said.
Why would a dieter's body rebel against weight loss? It's an evolutionary holdover from earlier times, when weight loss could threaten survival and reproduction, says Dr. Rudolph Leibel, an obesity expert at Columbia University in New York. So “it's not surprising at all” that our bodies would fight back for at least a year, he said. “This is probably a more or less permanent response.”
People who lose significant weight not only gain bigger appetite but also burn fewer calories than normal, creating “a perfect storm for weight regain,” Leibel said.
He said avoiding weight regain appears to be a fundamentally different problem from losing weight in the first place, and that researchers should pay more attention to it.
The study was supported by the Australian government, medical professional groups and a private foundation. Proietto served on a medical advisory board of Nestle, maker of Optifast, until last year.
<한글 기사>
요요현상은 호르몬 때문
다이어트로 어렵게 체중을 줄여도 나중에 다이어트 이전의 체중으로 되돌아가는 이른바 요요현상의 이유가 밝혀졌다.
호주 멜버른 대학 의과대학의 조지프 프로이에토(Joseph Proietto) 박사는 요요 현상은 다이어트를 시작하면서부터 체중을 줄인 이후까지 식욕과 관련된 9가지 호르 몬 분비가 체중증가에 유리하게끔 줄어들거나 늘어나기 때문이라고 밝힌 것으로 헬스데이 뉴스가 26일(현지시간) 보도했다.
프로이에토 박사는 10주간의 다이어트로 체중을 10% 줄이는 데 성공한 과체중 또는 비만인 사람 34명을 대상으로 다이어트를 시작했을 때와 끝냈을 때 그리고 그로부터 1년 후 3차례에 걸쳐 식욕관련 9가지 호르몬의 혈중수치를 측정한 결과 이 같은 사실이 밝혀졌다고 말했다.
위 내막세포에서 분비되는 식욕촉진 호르몬인 그렐린은 체중감소 후부터 계속 증가한 반면 식욕을 억제하는 호르몬인 렙틴은 감소했으며 다른 식욕관련 호르몬 수 치들도 체중증가에 유리한 쪽으로 변화가 나타났다고 프로이에토 박사는 밝혔다.
따라서 체중을 원하는 수준으로 끌어내렸다고 해서 전쟁이 끝난 것은 아니며 체중증가를 지속적으로 감시하면서 건전한 식사습관과 규칙적 운동을 통해 전쟁을 계속해야 할 것이라고 그는 강조했다.
이 결과는 장기적으로 배고픔을 억제하는 약의 개발이 해결책임을 시사하는 것 이라고 프로이에토 박사는 덧붙였다.
이에 대해 로스앤젤레스 캘리포니아 대학 인간영양연구실장 데이비드 히버 박사 는 인간은 배고픔에는 잘 적응하지만 과영양에는 적응하기 어렵기 때문이라고 논평 했다.
이 연구결과는 미국의 의학전문지 '뉴 잉글랜드 저널 오브 메디신(New England Journal of Medicine)' 최신호(10월27일자)에 발표되었다.
