Fat: Friend or Foe?
The Skinny on Low-Fat Diets

July 22 —
Dr. Tim Johnson
For the past 30 years, Americans have been religiously following low-fat diets. But as a nation, we've actually been getting fatter. So nutrition experts are finally asking: Do low-fat diets really work?
"The theory was that a low-fat/high-carb diet would help control weight and prevent killer diseases," says ABCNEWS Medical Editor Dr. Tim Johnson. "Unfortunately, most of the studies that followed did not show a direct link between fat in the diet and heart disease or cancer."

Johnson has the skinny on a diet revolution sweeping the country that might be the answer for overweight Americans. He joined ABCNEWS.com for a live chat on Monday, July 22.

Moderator
Dr. Tim, welcome. Thanks for joining us.

In a recent New York Times article, science writer Gary Taubes attacked what he considers the "bad science" that has lured millions to low-fat diets.

What is the science behind the low-carb dietary recommendations?

Dr. Tim Johnson
That science is lacking at this point. There are short-term studies that show a benefit from a low-carb diet. Indeed, last week respected researchers at Duke released a short-term study showing the benefits of a low-carb diet.

However, everyone acknowledges what we need now are the long-term studies that were never done with the low-fat diet. Fortunately, there are now several of these long-term studies being started.

Moderator
Are low-carb diets right for everyone? What about people with high cholesterol or diabetes?

Dr. Tim Johnson
That's one of the questions that has to be answered by these long-term studies. Again, there is some short-term evidence that low-carb diets could be beneficial for people with diabetes. That makes intuitive sense, given the connection between sugar intake and insulin level.

It is unlikely there will ever be one type of diet that is best for everyone. But I personally believe that a low-refined carb diet will prove to be more beneficial for more people than low-fat diets have been.

Moderator
Brenda writes: "I am currently a family and consumer education teacher in a middle school. I have been teaching my students for years the basics of the food pyramid. Where do I go from here?"

Dr. Tim Johnson
That's a very good question. I would say that it is time to start modifying the food pyramid away from the refined carbs and starches which are at the broad base of the pyramid and instead encourage more nutritious carbs found in fruits, vegetables and whole grain products.

If you want more information on this particular subject — the food pyramid — I would strongly recommend Dr. Walter Willett's book, Eat, Drink and Be Healthy. Walter is the chairman of the Department of Nutrition at the Harvard School of Public Health. I think his book is the best book on nutrition currently available.

Betty asks:
When a person switches to the newly advised low-carb diet with more fruits and vegetables, lean protein, etc., how long before the blood sugar (getting hungrier and hungrier because of the sugar intake) will equalize and there will be more physical satiation?

Dr. Tim Johnson
That will vary from one person to another. Some people notice an almost instant change in hunger levels. Others will report modified hunger levels, but not the absence of hunger.

Also, adding some "good" fats to the diet — for example, various olive oil-based products and whole grain rice and bread — can also help with satiation.

Chris asks:
Why was the word calorie never mentioned in your story? Isn't calories what make you gain or lose weight?

Dr. Tim Johnson
You make a good point. We probably should have included the word "calories" because they do indeed ultimately make a difference. The point is that a good fat/good carb diet should reduce hunger which in turn should reduce calorie intake.

CJ asks:
What is the scoop on hydrogenated fats? Should we avoid things that contain "partially hydrogenated vegetable oils?" Does the hydrogenation make the good oils actually bad for you?

Dr. Tim Johnson
Yes they do. Hydrogenating plant oils turns them into solid fats that are easier for cooking and storage but bad for us health-wise. These "partially hydrogenated" oils are also known as trans fatty acids.

It is my understanding that in the very near future, food products will be required to list the actual amount of trans fatty acids instead of simply putting "partially hydrogenated" on the label.

Chad H. asks:
As a college student on a limited budget who is also overweight, what advice can you give for quick foods that are really good for you? (In light of this story). Apparently, Ramen isn't as good for us as previously stated...

Dr. Tim Johnson
I would advocate fruits and vegetables as quick snacks. You don't have to cook them. All you have to do is wash them and put them in your mouth. I'm eating a peach right now, and it's filling me up!

Tamara asks:
The diet includes eating a lot of meat. What can I do, since I am a vegetarian?

Dr. Tim Johnson
First, I wouldn't agree that the new recommendations involve eating "a lot of meat." They would include eating reasonable portions of lean meat, fish and chicken. It is certainly possible to eat a healthy vegetarian diet without any of those proteins, but you have to know what you're doing to make sure you get a complete array of essential amino acids from various vegetable and legume products.

If you haven't already done so, I would strongly urge a consultation with a dietitian or nutritionist to help you come up with a healthy vegetarian diet.

George asks:
On the show they mentioned marbled meats as a no-no. Which meats are marbled and which are OK to eat?

Dr. Tim Johnson
Marbled meats refer to meats with a lot of fatty streaks in them such as certain steaks and certain other beef products. I would instead advocate eating fish, especially fish rich in Omega-3 fatty acids like salmon, and chicken without the skin.

Donna Edwards asks:
What about eggs? Do we now avoid them, limit them, or throw away the yolks?

Dr. Tim Johnson
The absolute safest course would be to throw away the yolks, because they're the part that's rich in cholesterol. Short of that, I would still limit your egg intake to no more than one per day on average.

However, the most important sources of cholesterol in our blood stream are usually not cholesterol-rich foods like egg yolks, but saturated fats that get converted into cholesterol by our body.

Kim asks:
Does caffeine cause weight gain?

Dr. Tim Johnson
The impact of caffeine on our hunger levels is quite variable from one person to another. However, the immediate effect of caffeine is often very mild weight loss since caffeine acts as a diuretic that promotes water loss through increased urination.

In some people, caffeine acts as a stimulant to hunger; in others, it seems to lessen hunger.

John Sherman asks:
What about the sugar content of alcohol? In a low-carb diet, what is the recommended consumption of alcohol?

Dr. Tim Johnson
Well, the overall recommended consumption of alcohol apart from carb levels is no more than 1-2 average-sized drinks per day. That level of alcohol consumption seems to protect against heart disease without causing other serious side effects.

However, larger consumption of alcoholic beverages definitely increases caloric intake because of the carbohydrates, especially in beer, which is why we rightly observe so-called "beer bellies" as a result.

Jibber asks:
I just saw your segment on the "the big fat lie." Are there any efforts or new plans to get rid of the food pyramid with a new one?

Dr. Tim Johnson
I honestly don't know what is going on in the inner circles of the U.S. Department of Agriculture which produces the government's food pyramid. However, I expect we will see some modifications in the food pyramid and in some other official recommendations over the next few years.

Kathy Fowler asks:
Where can I find a comprehensive list of the foods I should be eating and avoiding?

Dr. Tim Johnson
I will mention two resources. One is the very comprehensive book on nutrition I mentioned earlier by Dr. Willett. If you want a very short summary of modern nutritional information I would recommend my book on Men's Health which has a chapter on nutrition that is obviously applicable to both men and women. The book is called Dr. Timothy Johnson's OnCall Guide to Men's Health. Sorry for the shameless plug.

Moderator
Thanks to ABC's Dr. Tim Johnson and all those who joined the chat! If you'd like to join another live discussion, please visit our community index.

Moderated by ABCNEWS.com's Saira Stewart