So how do we find that critical balance that will provide us with the carbohydrates we need, while avoiding the excess consumption that can have such dire consequences?

The glycemic index, developed by researchers at the University of Toronto in Canada, is one guidepost. It assigns a numerical value to the impact each food has on blood sugar; the higher the reading, the greater the impact. Hundreds of foods have been tested for their impact on blood sugar, and the results have turned nutrition science on its head.

Let’s look, for example, at the first three carbohydrates we mentioned — broccoli, the bowl of sugar, and the baked potato. Here’s how they fare on the glycemic index. Raw broccoli skates in with a glycemic number of zero. Table sugar weighs in at 61. The baked potato is the heavy hitter — a russet baker comes in at 94 because it’s loaded with glucose, a plant-based sugar that is responsible for the level of sugar in our blood. Glucose is the building block of starches, and potatoes are a very starchy food. Carrots also have a high reading.

The solution would seem to be to load up on broccoli, go easy on the sugar, and avoid carrots and potatoes. Health experts would certainly love to see Americans eat more broccoli, and they wouldn’t care if we never ate another spoonful of sugar. But avoiding glucose completely isn’t the answer either.

For one thing, we would die without it. “Blood sugar is normally the only fuel used by the brain and central nervous system,” kinesiology professor Jack Young says. Glucose also powers our muscles. “If blood sugar goes too low, as it sometimes does in individuals with type I diabetes who overdose on insulin, you can end up comatose or dying.”

Nor do you have to give up the carrots or the baked potatoes. Kruskall says, “Carrots have a high glycemic index, but you would need to eat an enormous bowl of them to raise your blood sugar. If you throw a handful of carrots into your stir fry, that won’t raise your glycemic index. And carrots are good for you.”

What else is on your plate when you eat a high glycemic index food also matters. “If you eat a baked potato by itself, your glycemic index may rise, but if you make it part of a meal, you’ve diluted the glycemic impact. And potatoes have fiber and vitamins, and they provide energy,” she says.

Also remember that each of us is a bit different biologically from the person next to us. “One person may have his blood sugar raised by pasta, but not by orange juice,” says Kruskall. “Another person may have the reverse reaction.”

The bottom line, as in most things, is to employ moderation. Carbohydrates are essential to your diet, but don’t overdo.

So, if we now know what’s good for us and what’s not, where have we gone wrong?

For one thing, our consumption of carbohydrates has increased at a blistering pace in recent years. At one time, red meat was believed to be the enemy of healthy living because of its suspected link to heart disease. As a result, many people cut back on steak and eggs and began to bulk up on carbohydrates — more bread, more white rice, and more potatoes. At the same time, they guzzled a lot of sugar-laden soft drinks and carbohydrate-based convenience foods.

According to researchers from Harvard University’s School of Public Health, the carbs we consume the most include potatoes, rice, pizza, pasta, pancakes, sugar, jam, french fries, soft drinks, candy, sugary fruit juices, apples, and bananas. Not all of them are the best choices.

And what has been the result of this unprecedented carbohydrate consumption?

Not surprisingly, as our consumption of carbohydrates has shot upwards, so has the instance of type II diabetes.

In the 1980s, experts began to look not just at the number of calories various carbohydrates delivered, but at the impact they had on blood sugar levels. Wild swings in this critical benchmark can help destroy the pancreas, which produces insulin, an essential hormone. When your pancreas fails, you become diabetic.

Unfortunately, our modern diets cause rapid spikes in blood sugar, which induce the pancreas to produce big shots of insulin to help the body process its food.

Carbohydrates stimulate insulin production more than fats or proteins, and certain carbohydrates force insulin production into overdrive. This endangers our health two ways. High insulin production can cause heart disease and lead to type II diabetes.

The type II diabetes epidemic is particularly alarming because it has hit so many young people. “Type II used to be called adult onset diabetes because we rarely saw it in people under age 35,” Young says. “Now we see it in children as young as 8, 9, and 10.”

Part of the blame for the surge in type II cases lies with obesity. Though the mechanism isn’t fully understood, doctors have long observed that obesity and type II diabetes often occur in tandem. And it’s no secret why many of us gain weight — we often slug down huge amounts of highcalorie foods from the supermarket, from vending machines, and from the fast food restaurants that serve us big portions at a low price.

“Kids are eating more and more fast food,” says Kruskall. “Often fast food franchises are in school lunch rooms. At dinner, in households where finances and time are limited, you can get a lot of calories for three bucks at a fast food restaurant, and for another 39 cents you can upgrade your meal size and get another 1,000 calories.”

But, she says, the actual volume of food in these high-calorie meals isn’t large. A cheeseburger, fries, and a soda aren’t going to give you the same feeling of fullness as a nutrient-rich meal of chicken, green beans, brown rice, and milk. “So you may eat even more of the junk food,” Kruskall says.

As type II diabetes begins to develop, the problem snowballs. “The body continues to produce insulin, but the body’s tissues refuse to recognize that it’s there,” Young says. “So the pancreas produces more and more insulin trying to get the job done. Eventually, the pancreas can burn out.”

So what’s the solution?

Exercise is critical, and common sense would say to go easy on the carbohydrates that are likely to tax the pancreas and put on the pounds — a jelly donut with powdered sugar on top, for example.

But Young and Kruskall maintain that a healthy lifestyle does not need to be draconian.

Once again, moderation is key. Fast food doesn’t have to go completely, and we don’t have to sweat three hours a day on a treadmill.

“Incorporate physical activity into your lifestyle,” Young says. “Walk to the Starbucks instead of hopping in the car.”

And scale back on those portions. “You don’t need to have the three-taco lunch with the giant drink,” Kruskall says. “Try one taco and a diet drink.

“Even small changes can produce noticeable results.”