When's the best time to eat dessert? And other questions you have about sugar

Who doesn't want to get in shape for summer? But when it comes to what we should and shouldn't eat, the advice gets very confusing.

We used to be told to count calories...then we were counting carbs.

But more recently, the focus has been on sugar and its negative effect on everything from our daily health to our longevity.

So does that mean goodbye to the summer ice cream cone or the all-American apple pie? Or could sugar be not quite as bad as its reputation? To find out, we checked in with Dr. Steve Chaney, UNC Professor Emeritus and author of "Slaying the Food Myths," and got his opinion about this not-so-sweet anti-sugar trend.

Dr. Steve Chaney:

Let's start with something most of us we can all agree on: Americans are eating way too much sugar.

This excess sugar, along with other excesses, is part of what's is fueling the obesity epidemic. Obesity, in turn, is contributing to the increase in type 2 diabetes. Obesity also increases our risk of heart disease, hypertension, and some forms of cancer.

Most also agree that we should decrease the amount of added sugar in our diet. The disagreement comes when we start discussing the best way to do that. That's because there are so many inaccurate sugar myths circulating on the internet and in popular diet books. Let's look at some common sugar myths and separate fact from fiction.

MYTH:High fructose corn syrup is bad for you. Other sugars like honey, agave sugar, coconut sugar, and fruit sugar are healthier choices.

FACT: There are no sugar villains. There are no sugar heroes.

To banish this food myth, we need to look no further than the chemical composition of some common sweeteners sugars.

Most common sweeteners are a combination of fructose and glucose. High fructose corn syrup ranges from about 40 percent fructose to 50 percent fructose. The exact percentage depends on what kind of food product it is being added to. Honey and coconut sugar are about 45 percent fructose. Sucrose and grape juice concentrate are around 50 percent fructose. Apple juice concentrate is around 60 percent fructose, and agave sugar comes in at a whopping 80 percent fructose.

In other words, if fructose is the culprit that everyone makes it out to be, "healthy sugars" are no better than high fructose corn syrup. Simply substituting a "healthy sugar" for high fructose corn syrup is unlikely to provide any meaningful benefit.

MYTH: Diet sodas are the answer

FACT: Diet sodas, foods aren't helping us control the obesity epidemic

Are diet foods really working?

Most of the studies on diet foods have been done on diet sodas, so let's focus our attention there. Several recent studies suggest you gain just as much weight on diet sodas as on regular sodas. Even worse, because weight gain is the same on regular and diet sodas, the increased risk of diabetes and heart disease is also the same. This is a controversial area of research. Not all studies agree. However, a recent review of all the major studies in this field concluded there is no convincing evidence that diet sodas help you lose weight or prevent the diseases associated with obesity.

Why is that? Some experts think the cause is physiological. The sweet taste of the artificial sweeteners stimulates our appetite. Other experts think it is psychological. We feel virtuous for consuming a calorie-free soda and think that gives us license to eat more of the foods we love. Dr. Barry Popkin, a colleague from UNC-CH, calls it the "Big Mac and Diet Coke" mentality.

In summary, it has become increasingly clear in recent years that diet sodas are not the magic solution to weight control that everyone had hoped they would be. The diet versions of our favorite junk foods and convenience foods have been less studied. However, the evidence we do have suggests they may not be any better than the sugar-laden foods they replace.

MYTH: We should avoid sugars

FACT: It is the food, not the sugar.

If medium apples came with a nutrition label, you would discover that apples have about the same amount of sugar and the same percentage of fructose and glucose as an 8-ounce soda. Yet clinical studies tell us sodas are bad for us and apples are good for us.

Some of us have trouble with certain fruits. However, for most of us, fruits and naturally sweet vegetables are perfectly healthy.

So why is an apple full of sugar better for us than a soda?

As a biochemist, I am often tempted to delve into the fascinating details of human metabolism. In the interest of brevity, I will resist that temptation. Let me just say that whole foods like an apple contain fiber and protein which slow the absorption of sugars into our bloodstream. When these sugars enter the bloodstream slowly, we can metabolize them in a natural and beneficial manner. In other words, our metabolism and the foods we were designed to eat are perfectly matched.

However, when we consume sugar-containing sodas and junk foods, there is no fiber and protein to slow the entry of sugars into the bloodstream. We overwhelm our body's ability to process them in a healthy manner. This is when we start to experience the bad effects of sugars. In fact, all the studies showing the bad effects of high fructose corn syrup and other sugars have all been done with sodas and junk foods. They have not been done with apples and other naturally sweet whole foods.

MYTH: We have to give up dessert

FACT: It is the meal, not the sugar.

Let me throw you a lifeline here. You are probably wondering whether you also need to give up all your favorite pastries and desserts. You should certainly reduce them.

You should think of fresh fruit first when you think of a snack or a dessert.

But there is one secret you should know.

A dessert consumed along with a meal containing lots of fiber and some protein will have much less of an effect on blood sugar than the same dessert item consumed between meals. Of course, portion size is key. If you are ordering a piece of pie or cake at your favorite restaurant, why not split it with two or three of your friends? There will be plenty to go around.

MYTH: We should reject processed foods containing any sugar.

TRUTH: It is the food, not the sugar.

You have been told to scan the label of every processed food in the store. You have been told all the ways that sugar can be described on the nutrition label. And, you have been told to avoid processed foods that contain any sugar.

I agree we would all do well to cut back on processed foods and eat more whole foods instead. But, what about the "healthy" processed foods. There are processed foods with natural ingredients that provide some real benefits. Examples might be protein shakes to help you lose weight or snack bars to take with you when you are hiking. We certainly don't want foods that contain artificial sweeteners. We would also prefer not to have them taste like cardboard.

Fortunately, the same principle applies to processed foods that applies to whole foods. If they contain the right amounts of fiber and protein, sugars will enter the bloodstream slowly as nature intended. The key is to look for the term "low glycemic" on the label.

This term simply means the product contains the right balance of sugar, fiber, and protein so that it has very little effect on blood sugar levels. In short, you do still need to read labels. But, instead of trying to be a sugar detective you should be looking for "low glycemic" on the label.

Dr. Steve Chaney is Professor Emeritus at UNC Chapel Hill, and former Distinguished Professor in the Department of Biochemistry and Biophysics and the Department of Nutrition. He is also the author of the book "Slaying The Food Myths."