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Low Carb Diets: Are They Safe?

Posted Aug 24 2008 1:49pm 1 Comment
CHERYL WILLS: I'm Cheryl Wills. Welcome to our webcast. Many people try low carb diets to try to beat the battle of the bulge, but how effective are these popular diets, and more importantly, how safe? During this webcast we'll go over some of the pros and cons of this controversial weight loss method.

Joining me to discuss this issue is Samantha Heller. She's a registered dietitian and a Senior Clinical Nutritionist at New York University Medical Center. Thanks for joining us Samantha.

SAMANTHA HELLER: I'm happy to be here.

CHERYL WILLS: Also here, Martha McKittrick. She's a registered dietitian at New York Presbyterian Hospital in New York City. Martha, thank you.


CHERYL WILLS: You know, we hear the word carbohydrate a lot. It's on the back of most foods. A lot of people, I fear, do not know exactly what a carbohydrate is and what it means for your body. So, let's define it. What is a carbohydrate?

SAMANTHA HELLER: A carbohydrate is one of the major nutrients that our bodies use to provide energy. We know of carbohydrates. Generally, we think of them as starches like potatoes, and bread and past. But, carbohydrates are also vegetables, fruits, legumes, and we want them to be a greater percentage of our diet because that's the major fuel that our body uses to function.

CHERYL WILLS: And it breaks down.

SAMANTHA HELLER: Carbohydrates break down in your body. Finally, after they go through all their breakdown, they wind up as sugar, known as glucose, in your blood. That's the very basic unit of which a carbohydrate is made.

CHERYL WILLS: Sure. Martha, we have two different types, simple and complex. Define simple for me. What is a simple carbohydrate?

MARTHA MCKITTRICK, RD, CDE: A simple carbohydrate is basically something that's found in a sweet food. It would be found in regular soda, jam, jelly, table sugar. Basically, when you eat something that has simple carbohydrate in it, it breaks down rapidly into sugar. Your blood sugar is elevated quite quickly after eating the food.

CHERYL WILLS: Define complex. What is that?

MARTHA MCKITTRICK, RD, CDE: The basic difference between a complex and a simple is that a complex carbohydrate is a whole bunch of simples hooked together in a chain. When you eat something, which is a complex carbohydrate, which would be found in rice, bread, past, potatoes, it will break down to sugar, but it takes longer than the simple.

CHERYL WILLS: That would be refined. Is that correct?

MARTHA MCKITTRICK, RD, CDE: Right. Now, there are two different kinds of complex. There is refined, and there is unrefined.

CHERYL WILLS: Please define refined?

MARTHA MCKITTRICK, RD, CDE: Refined is basically something that's been processed. I usually call it a white carbohydrate. Again, white pasta or white bread. Unrefined has not been processed. It has more fiber in it. The more unrefined a carbohydrate is, the longer it takes to break down into sugar. Because of the fiber, it slows it down. When you eat an unrefined, it turns to sugar more slowly, so your blood sugar goes up much more slowly versus the complex refined, which it goes up more quickly, versus the simple, which it goes up very quickly.

CHERYL WILLS: Samantha, low carb diets are very popular these days. There are so many books. There are so many different anecdotes out there about what you should eat/not eat. What's the rationale behind a low carb diet?

SAMANTHA HELLER: It's a rationale that I think varies depending on the author of the book. I think when someone chooses or goes on a low carb diet, what they are doing is cutting out almost an entire food group. Any time you do that, you're going to be cutting out calories, so you tend to lose weight. Carbohydrates also hold water, so when you drop a lot of those carbohydrates out of your diet, you're going to start to lose water out of your body quickly. Our bodies are made up of mostly water, so when you start losing that water that the carbohydrate holds onto, you lose weight. And you think, "I'm losing weight." Well, what does that weight consist of? Is it fat? Is it protein? Is it water?

CHERYL WILLS: What are you losing?

SAMANTHA HELLER: Initially, you're losing water. Then maybe over time, if you're losing numbers of pounds, some fat. Then, what I find very scary, you're going to start losing protein. You're body wants to spare carbohydrate because it's the fuel it needs to support your brain and your muscles. So, you'll start breaking down protein. Guess what's made of protein? Your heart and your muscles.

I think both Martha and I would agree that the healthiest and best diet is a balanced diet. You don't want to cut out any total food group.

CHERYL WILLS: Martha, there are so many people who are involved in low carb diets. They are losing weight. You see them all over the television and magazine ads. How healthy are they?

MARTHA MCKITTRICK, RD, CDE: My concern is more on the long-term. I don't really have a problem with somebody following a lower carbohydrate diet for a few weeks. That can actually get some momentum going. Like Samantha said, you lose a lot of water. But then you have to go into a balanced diet. I recommend a diet that has at least 50% carbohydrate. My concern is that long-term, if you omit fruits, vegetables, whole grains, you're omitting vitamins, minerals, fiber, cancer fighting phytochemicals. You're setting yourself up for a disease in the long run. So long run, I think they're much more dangerous.

CHERYL WILLS: Sure. So you're saying people can have a problem sustaining it also?

MARTHA MCKITTRICK, RD, CDE: They're also very difficult diets to be on. Most peoples' favorite foods are some kind of carbohydrate, whether it's pasta, bagels, pretzels or whatever. Now you're on a diet that excludes all of your favorite foods. You might be able to do it for a few days or maybe a few weeks at most, but most people end up binging or even gaining more weight because you feel so deprived.

It also alters some of your brain chemicals. When you seriously cut out carbohydrates, you alter your brain chemicals, and you are really going to crave carbohydrates. It's a difficult thing, and there is no need to do it.

SAMANTHA HELLER: I totally agree with her. I would also like to bring out the point that low carbohydrate is sort of a relative term, unless you're looking at the numbers in the books. For one person, high carbohydrate might be three cups of pasta. So, low carbohydrate to them might be cutting that portion in half. What we're discussing is really moderate, intelligent portions. So, instead of having an extra large thing of French fries, have a small one, or a baked potato. The portion size is really an issue with carbohydrate. It's easy to eat a lot of them.

CHERYL WILLS: How do you know when it's getting dangerous? You have some people who are on these low carb diets for a long period of time. How do you know when you're entering that danger zone?

SAMANTHA HELLER: There are signs if you're going to enter something called ketosis. Ketosis happens when your body says, "Uh oh, I'm running out of fuel." So it goes to an alternate source for fuel. No carbohydrate for fuel. It's going to start breaking down fat and forming something called the ketone body. Your breath gets fruity and it doesn't smell good. Some people get a coating on their tongue. Some people may get slightly confused. If it accelerates, then you can really be into trouble because the whole acid-based balance in your body goes off.

CHERYL WILLS: Define for our viewers what a ketone is.

SAMANTHA HELLER: A ketone is a byproduct of breaking down fat for energy. It's the only other source that your brain can use for fuel. It's like if you run out of gas for your car, what is the last resort thing you can use? Your body is freaking out a bit, saying, "Okay, let's make those ketones so we can at least use our brain to have our bodies function."

CHERYL WILLS: Martha, a lot of people with a lot of diets put the weight back on after they give up on it. Is that the case also with low carb diets? Do they put the weight back on after they stop?

MARTHA MCKITTRICK, RD, CDE: I would say that they do. There was a major study done. I believe it was the National Weight Control Registry. They interviewed over 3,000 people. The purpose of the study was to find out who maintained their weight loss. Out of those people who did, how did they keep the weight off. They found out that the majority of people followed a balanced type of diet. I think they averaged about 1,400 to 1,500 calories. Very few of the people followed low carbohydrate types of diets. Pretty much, they all exercised. I think that what that's showing us is the way you keep the weight off is to eat a healthy, balanced diet where you're not depriving yourself and omitting food groups, exercise and cut the calories down. Cut down your portions.

The bottom line is calories. Carbs aren't the bad guys. Portion sizes are. When you eat an eight-ounce muffin, a jumbo muffin that we see here in New York a lot, it's 800 calories. A jumbo bagel is 400 or 500 calories.

CHERYL WILLS: Don't put butter or anything else on it.

MARTHA MCKITTRICK, RD, CDE: Forget the butter and the cream cheese. Even a tuna salad sandwich can be 700 calories. A slice of pizza is 500. So, it's not the carbs that are the bad guys, it's the amount of food we're consuming. We're eating way too much food.

CHERYL WILLS: But some people do well on low carb diets. They get involved with the food pyramid.

MARTHA MCKITTRICK, RD, CDE: Lower. I believe that. I don't think people have to be on real low carbohydrate diets. I think maybe lower. Where the food pyramid is recommending about 55% to 60% of calories coming from carbs, some people might do better on 40%. Does that mean we need to go as far as some of the diets recommend, to 20%? Do we need to go into ketosis? No. It can be dangerous. There is no need to do it. If you're having a hard time losing weight on the standard higher carbohydrate, cut it a little bit. But more importantly, watch your portion sizes and exercise. You should be able to lose the weight.

SAMANTHA HELLER: Also, some of the low carb, high protein diets, what they advocate is high fat; high saturated fat. Cheese and meat and butter. People say, "Oh, I'm so happy I can eat all of this and I'm losing weight." Yes, because you're cutting out the food group. But, what is it doing to your arteries? That's what I think both Martha and I find pretty scary. It's not just low carb, but they're eating high fat and high saturated fat.

I think what we're both advocating is to just balance; not a lot of fat, not a lot of saturated fat, not a lot of carbohydrate. Just balanced meals.

CHERYL WILLS: Are there certain people who should just flat-out stay away from low carb diets? People with certain types of illnesses, I assume? Say diabetics?


CHERYL WILLS: What about people with heart disease who would consume a lot of these meats.

MARTHA MCKITTRICK, RD, CDE: As Samantha said, I think more of the concern is the kinds of fats that they're eating. If somebody with heart disease is having a little more fat, but it's in the form of an olive oil or something unsaturated, I'm not really concerned with that. I'm more concerned with somebody who has heart disease who is loading up on saturated fats, on cheese and ice cream and bacon and eggs. That's more of a concern for me.

CHERYL WILLS: You mentioned one study. But, have there been enough studies, Martha, about low carb diets?

MARTHA MCKITTRICK, RD, CDE: That's a problem. I have not read any long-term studies that would show what could happen to somebody if they were on a very low carb, high fat diet for many years. I don't believe there have been any studies done. We know short-term that you can lose weight. But the question is, what happens if you're on this diet for life and you're omitting your fruits and vegetables and whole grains? Is that going to affect your health? We don't know.

It would seem that it would. We do not have studies to show that. Therefore, I would be very leary of recommending somebody follow a real low carb, high fat diet.

CHERYL WILLS: Samantha, do you think that there should be more studies, being that millions of people are doing it anyway?

SAMANTHA HELLER: This is an interesting point, and I'm treading on thin ice here. What I would say is that one of the reasons there is not a lot of studies is because it's hard to define the variables. Another reason is that we know by common sense and by a whole host of scientific literature that eating a high saturated fat diet and cutting out carbs for a long time is dangerous for your health. I think one of the reasons there aren't a lot of studies is because it's unethical. For me to say, "Cheryl, go have some cream and some butter and cheese and don't eat this. Eat that. Eat that. You'll lose weight." I'm being unethical. I may be making some money, but I'm not telling you what's best for your health. I don't really think you could get someone to fund a study to do that if you're telling people to do something that you really know is not good for them.

CHERYL WILLS: I guess the bottom line is that people should get a dietitian or check with their doctor before doing any kind of weight loss program.


CHERYL WILLS: That should be the take home message. Check with your doctor, dietitian or nutritionist – there are many of them out there – before getting involved with any diet program.

Thank you for tuning into our webcast. I'm Cheryl Wills.

Comments (1)
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interesting i am trying to get my brother to eat carbs but he believes if he does he'll stop losing weight. we are a big family who surprisingly eat healthy and exercise! the only time we lose weight is with tony furgerson, which is a shake diet with an evening meal at night of meat and vegies. We have all tried other diets aswell as eating smaller portions, but its not our portions thats the problem as we only have half a plate each at dinner and when not on tony fergurson only eat a bowl of natural meusli and fruit for breakfast and a wholemeal sandwich for lunch. so why are we big? it is not fair! i think we just dont break down carbs or something i guess maybe we are alergic to them? chips, lollies, chocolate is only eaten as a rare treat and we dont eat ANY saturated fats other than these rare occasions. please help us!
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