Periodic Fasting May Cut Risk of Heart Disease, Diabetes

Despite Health Benefits, Fasting May Not Be for Everyone, Doctors Say

Medically Reviewed by Laura J. Martin, MD on April 05, 2011

April 5, 2011 -- Occasional water-only fasts may lower your risk of heart disease and diabetes, according to new research presented at the annual scientific sessions of the American College of Cardiology in New Orleans.

The study was conducted in Salt Lake City, where two-thirds of the residents are Mormons who fast once a month for 24 hours for religious purposes.

In a previous study, the same team of researchers found that people who answered "yes" to the question “Do you abstain from food and drink for an extended time?” had a lower prevalence of coronary disease.

Now researchers were able to replicate and expand upon these findings. “People who fast have lower rates of coronary disease, and fasting was associated with a lower prevalence of diabetes,” says study leader Benjamin D. Horne, PhD, MPH, director of cardiovascular and genetic epidemiology at the Intermountain Medical Center Heart Institute in Salt Lake City.

The state of Utah consistently has some of the lowest rates of heart disease in the U.S., and until now many believed it was because the Church of Jesus Christ of Latter Day Saints - the official name of the Mormon Church -- teaches its disciples not to smoke.

“The common wisdom has been that nonsmoking has protected Utahans from cardiac disease, but as smoking rates dropped across the country, Utah’s heart disease rate was still the lowest,” he says. Horne’s preliminary research suggested it could be the fasting that promotes the health benefits, and the new study substantiates that work.

Blood Fat Levels Measured During Fasts

In a companion study presented at the same meeting, the team looked at blood markers for heart risks among people who had not previously fasted over 12 hours. The blood markers were checked when they fasted and during a normal eating day. The fast was a water-only fast, and participants were allowed to take any necessary medication.

The participants’ HDL "good" cholesterol rose during the fast. Their LDL “bad” cholesterol levels and their total cholesterol levels also increased, which is not considered favorable.

During the fast, participants also saw reductions in levels of dangerous blood fats called triglycerides and blood sugar or glucose levels.

“Your body goes into self-protection mode to preserve the integrity of cells and tissue until food starts coming in again, so it uses fats instead of glucose for fuel,” Horne says.

The increase in total cholesterol may just be transient.

“It appears that the total cholesterol has gone up because the liver is not processing as much cholesterol and instead it is being dumped into the bloodstream to be used as fuel,” he says.

“We need to answer a lot of questions to be able to connect all these dots,” he says.

“We know from our tests that these patients had a lower prevalence of diabetes and coronary disease and now we are backing up to see the mechanism,” he says.

Do Juice Fasts Count?

Many so-called “fasts” -- such as "juice" fasts -- are widely promoted on the Internet.

Comparing the water-only fasts to these juice fasts is apples to oranges, Horne says.

“These juice fasts and cleanses could have a similar effect to caloric restriction,” he says. “In animal studies, reducing the amount of daily calories by 40% to 50% has a benefit on your heart, but it is not as strong of a benefit as [water-only] fasting,” he says.

“Fasting is not a quick fix, it’s a long-term lifestyle that you integrate into your normal life and do it for the duration,” says Horne, who says he fasts once a month.

Fasting is not for everyone. “There are some dangers for people that are at high risk for other conditions, women who are pregnant or lactating, and young children,” he says.

Other Views

Howard Weintraub, MD, clinical director of the Center for the Prevention of Cardiovascular Disease at NYU Langone Medical Center in New York City, says that the findings of elevated LDL and total cholesterol in the face of reduced heart and diabetes risk warrant further investigation.

“We need a lot more information about this,” he says.

The new study “tells us that we eat too much and we don’t need to eat quite so much,” he says. But “before I start advising my patients to fast, I need to see more information as to the other attributes of these study participants,” he says.

One of the dangers of an occasional fast is that it may be followed by a binge that negates all of the potential health benefits.

“It’s like having Diet Coke so you can have a cheeseburger,” he says. Or saying, “If I don't eat on Monday, no one will yell at me when I eat like a pig on Tuesday and Wednesday,” he says.

Suzanne Steinbaum, MD, director of women and heart disease at Lenox Hill Hospital in New York City, says you don’t need to fast to see beneficial changes in your heart disease risk factors.

“If you don’t eat bad foods, your profiles are better in terms of weight and blood pressure, and your triglycerides go down, and your blood sugar goes down,” she says, “Anything in the extreme is not the way to go. It’s how you eat on a daily basis that matters."

Her bottom line? “I don’t recommend fasting, but I do recommend getting rid of unhealthy foods in your diet as fast as you can.”

Show Sources


Howard Weintraub, MD, clinical director, Center for the Prevention of Cardiovascular Disease, NYU Langone Medical Center, New York City.

Suzanne Steinbaum, MD, director, women and heart disease, Lenox Hill Hospital, New York City.

Benjamin D. Horne, PhD, MPH, director, cardiovascular and genetic epidemiology, Intermountain Medical Center Heart Institute, Salt Lake City.

American College of Cardiology Annual Scientific Session, New Orleans, April 2-5, 2011.

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