저탄수화물 식단으로 체중감소와 심장 튼튼-뉴욕타임즈 기사

 9월 1일의 뉴욕 타임즈에 실린 어떤 건강 컬럼을 읽는 순간 아주 유익한 내용이라는 판단이 들었다. 건강 식단을 지양함에 있어

지방 섭취에 관한 보편화된 상식을 깨뜨리는 내용을 담고 있었다. 제목을 번역하자면 "지방을 포함한 저탄수화물의 식단을

주장한다."이다. 정확한 내용에 관심있는 사람을 위해서 기사 전문을 이 글 아래에 그대로 옮겼다. 요점을 정리하자면:

 

루이지아나주에 있는 투레인 의과 대학의 Lydia A. Bazzano 교수팀은 미국립보건원 (the National health Institute)의 지원을 받아 

다양한 특성의 150 명의 남녀를 골라서 식단과 심장의 관계를 일년 동안 연구했다. 참가자들을 두 그룹으로 나누어서 탄수화물 또는 

지방을 제한시키고 칼로리 섭취와 활동량은 동일하도록 했다.

 

*1 그룹: Low-fat group (저지방 식단 그룹, 고탄수화물 식단 그룹)

  하루 권장 칼로리에서 지방으로 부터의 섭취를 30% 미만으로 줄였다. 반면에 곡류, 시리얼과 전분류와 채소의 섭취는 늘렸다.

* 2 그룹: Low-carbohydtate (저탄수화물 식단 그룹, 고지방 식단 그룹)

  일일 칼로리 권장량에서 지방으로 부터의 섭취를 40% 이상으로 올렸다. 채소, 과일과 콩 종류의 섭취도 늘렸다.

  포화지방을 미국심장협회가 권장하는 총 지방량의 5-6%보다 높은 13% 까지 늘렸지만 지방의 50% 이상을 불포화지방 음식

  섭취에서 얻도록 했다.

 

결과:

탄수화물을 적게 먹고 트랜스 지방을 제외한 지방을 더 섭취한 사람이 체지방도 적고 심장질환도 적다.

즉, 칼로리를 염두에 두지 않고 탄수화물을 줄이면 몸무게는 줄고 심장은 더 튼튼해진다고 한다. 또 신진대사율도 높아진다.

 

좀 더 자세한 설명을 하자면:

  *저지방 식단 그룹의 참가자들은 약간의 체중이 감소했고 근육량은 크게 감소했다.

    Framingham risk score(10 년 안에 심장마비를 일으킬 위험 칫수)는 전과 변함없다.

  *저탄수화물 그룹은 저지방 그룹 참가자들에 비해서 평균 8 파운드 더 많은 체중 감소, 체지방의 감소, 근육량은 증가했다.

    또, 염증 수치 (inflammation)의 감소와 중성지방은 크게 감소, HDL (좋은 콜레스트롤)은 크게 증가,

    Framingham risk score 도 감소했다.

  *두 그룹 모두의 혈압, 총콜레스트롤, LDL (나쁜 콜레스트롤)의 수치는 비슷했다.

 

보통 우리는 지방은, 특히 포화지방은 해로운 것으로 알고있다. 1970년 대에

황제 다이어트라고 불리던  Atkin Diet 가 선풍적인 인기를 끌었다. 하지만

높은 지방과 단백질의 섭취가 콜레스트롤 숫치를 올리고 심장질환을

일으킨다는 혹평을 받았다. 

 

저탄수화물 식단은 아트킨 다이어트의 변형이라고 할 수 있다. 지방과

단백질 섭취량을 높이기 위해서 주로 불포화지방산인 생선, 올리브 오일,

너트의 섭취를 권하지만 치즈, 버터, 빨간색 고기와 같은 포화지방산도

허락한다. 그래서 좋은 식사의 예는 아침에는 달걀, 점심에는 튜나 샐러드, 저녁에는 소고기, 닭, 생선, 돼지고기, 두부와 같은

단백질을 풍부한 채소와 함께 먹는 것이다.

 

심장질환 예상 척도 (heart disease predictor) 는 혈관을 흐르는 LDL (나쁜 콜래스트롤) 입자의 크기와 숫자이다.

입자 수가 작고 많은 높은 밀도의 LDL인지, 아니면 크고 적은 저밀도의 LDL 인지는 매우 중요하다. 정제 탄수화물 (refined

carbohydrates)을 섭취하면 LDL 의 숫자가 많아져서 입자가 작은 고밀도로 변화한다. 반면에 포화지방은 LDL 입자를 크게

하지만 저밀도가 되기 때문에 혈관을 막지않고 떠돈다. 작은 입자의 LDL 은 중성지방이 높은 사람, 배가 볼록 나온 사람,

대사증후군을 앓는 사람, 동맥경화증을 가진 사람에게서 흔히 볼 수 있다.

 

 

 

A Call for a Low-Carb Diet That Embraces Fat

 

By ANAHAD O’CONNORSEPT. 1, 2014

 

People who avoid carbohydrates and eat more fat, even saturated fat, lose more body fat and have fewer cardiovascular

risks than people who follow the low-fat diet that health authorities have favored for decades, a major new study shows.

 

The findings are unlikely to be the final salvo in what has been a long and often contentious debate about what foods are

best to eat for weight loss and overall health. The notion that dietary fat is harmful, particularly saturated fat, arose

decades ago from comparisons of disease rates among large national populations.

 

But more recent clinical studies in which individuals and their diets were assessed over time have produced a more

complex picture. Some have provided strong evidence that people can sharply reduce their heart disease risk by eating

fewer carbohydrates and more dietary fat, with the exception of trans fats. The new findings suggest that this strategy

more effectively reduces body fat and also lowers overall weight.

 

The new study was financed by the National Institutes of Health and published in the Annals of Internal Medicine.

It included a racially diverse group of 150 men and women — a rarity in clinical nutrition studies — who were assigned to

follow diets for one year that limited either the amount of carbs or fat that they could eat, but not overall calories.

 

“To my knowledge, this is one of the first long-term trials that’s given these diets without calorie restrictions,” said

Dariush Mozaffarian, the dean of the Friedman School of Nutrition Science and Policy at Tufts University, who was not

involved in the new study. “It shows that in a free-living setting, cutting your carbs helps you lose weight without

focusing on calories. And that’s really important because someone can change what they eat more easily than trying

to cut down on their calories.”

 

Diets low in carbohydrates and higher in fat and protein have been commonly used for weight loss since Dr. Robert Atkins

popularized the approach in the 1970s. Among the longstanding criticisms is that these diets cause people to lose weight

in the form of water instead of body fat, and that cholesterol and other heart disease risk factors climb because dieters

invariably raise their intake of saturated fat by eating more meat and dairy.

 

Many nutritionists and health authorities have “actively advised against” low-carbohydrate diets, said the lead author

of the new study, Dr. Lydia A. Bazzano of the Tulane University School of Public Health and Tropical Medicine. “It’s been

thought that your saturated fat is, of course, going to increase, and then your cholesterol is going to go up,” she said.

“And then bad things will happen in general.”

 

The new study showed that was not the case.

 

By the end of the yearlong trial, people in the low-carbohydrate group had lost about eight pounds more on average than

those in the low-fat group. They had significantly greater reductions in body fat than the low-fat group, and improvements

in lean muscle mass — even though neither group changed their levels of physical activity.

 

While the low-fat group did lose weight, they appeared to lose more muscle than fat.

 

“They actually lost lean muscle mass, which is a bad thing,” Dr. Mozaffarian said. “Your balance of lean mass versus

fat mass is much more important than weight. And that’s a very important finding that shows why the low-carb,

high-fat group did so metabolically well.”

 

The high-fat group followed something of a modified Atkins diet. They were told to eat mostly protein and fat, and

to choose foods with primarily unsaturated fats, like fish, olive oil and nuts. But they were allowed to eat foods higher

in saturated fat as well, including cheese and red meat.

 

A typical day’s diet was not onerous: It might consist of eggs for breakfast, tuna salad for lunch, and some kind of protein

for dinner — like red meat, chicken, fish, pork or tofu — along with vegetables. Low-carb participants were encouraged

to cook with olive and canola oils, but butter was allowed, too.

 

Over all, they took in a little more than13 percent of their daily calories from saturated fat, more than double the 5 to 6 %

limit recommended by the American Heart Association. The majority of their fat intake, however, was unsaturated fats.

 

The low-fat group included more grains, cereals and starches in their diet. They reduced their total fat intake to less than

30 percent of their daily calories, which is in line with the federal government’s dietary guidelines. The other group

increased their total fat intake to more than 40 percent of daily calories.

 

Both groups were encouraged to eat vegetables, and the low-carbohydrate group was told that eating some beans and

fresh fruit was fine as well.

 

In the end, people in the low-carbohydrate group saw markers of inflammation and triglycerides — a type of fat  that

circulates in the blood — plunge. Their HDL, the so-called good cholesterol, rose more sharply than it did for people

in the low-fat group.

 

Blood Pressure, total cholesterol and LDL, the so-called bad cholesterol, stayed about the same for people in each group.

Nonetheless, those on the low-carbohydrate diet ultimately did so well that they managed to lower their Framingham risk

scores, which calculate the likelihood of a heart attack within the next 10 years. The low-fat group

on average had no improvement in their scores.

 

The decrease in risk on the low-carbohydrate diet “should translate into a substantial benefit,” said Dr. Allan Sniderman,

a professor of cardiology at McGill University in Montreal.

 

One important predictor of heart disease that the study did not assess, Dr. Sniderman said, was the relative size and

number of LDL particles in the bloodstream. Two people can have the same overall LDL concentration, but very different

levels of risk depending on whether they have a lot of small, dense LDL particles or a small number of large and

fluffy particles.

 

Eating refined carbohydrates tends to raise the overall number of LDL particles and shift them toward the small, dense

variety, which contributes to atherosclerosis. Saturated fat tends to make LDL particles larger, more buoyant and less

likely to clog arteries, at least when carbohydrate intake is not high, said Dr. Ronald M. Krauss, the former chairman of

the American Heart Association’s dietary guidelines committee.

 

Small, dense LDL is the kind typically found in heart patients and in people who have high triglycerides, central obesity

and other aspects of the so-called metabolic syndrome, said Dr. Krauss, who is also the director of atherosclerosis

research at Children’s Hospital Oakland Research Institute.

 

“I’ve been a strong advocate of moving saturated fat down the list of priorities in dietary recommendations for one reason:

because of the increasing importance of metabolic syndrome and the role that carbohydrates play,” Dr. Krauss said.

 

Dr. Mozaffarian said the research suggested that health authorities should pivot away from fat restrictions and encourage

people to eat fewer processed foods, particularly those with refined carbohydrates.

 

The average person may not pay much attention to the federal dietary guidelines, but their influence can be seen,

for example, in school lunch programs, which is why many schools forbid whole milk but serve their students fat-free

chocolate milk loaded with sugar, Dr. Mozaffarian said.