Not all carbohydrates are the same

In 1981 a Toronto researcher named David Jenkins, the same man who later built the Portfolio diet, ran an experiment that changed how people think about carbohydrate. He fed volunteers equal amounts of carbohydrate from fifty different foods and measured how fast and how high their blood sugar rose. The differences were enormous. White bread and potatoes spiked it fast. Lentils and barley barely moved it. He ranked them on a scale and called it the glycemic index.

The index measures the speed of the rise. The load, added later, measures the amount: a carrot has a high index but so little carbohydrate that its load is tiny; a plate of pasta has a moderate index and a large load. Together they give a picture that the old categories, simple versus complex, never did. A baked potato can spike blood sugar faster than table sugar. A bowl of steel-cut oats, with the same carbohydrate, barely does.

The practical rules. At each meal, choose the slower carbohydrate: whole intact grains over flour, beans and lentils over potatoes, fruit over juice. Pair carbohydrate with protein, fat or fiber, which slow it down; an apple with almonds has a lower effect than an apple alone. And notice that processing, more than the food itself, is what raises the index: the more ground, puffed and refined, the faster it hits.

It's the table key that sits between the low-carb keys and the plant-based ones and makes peace between them. You don't have to cut carbohydrate. You have to choose the kind, and slow it down. For blood sugar, energy, and hunger, that one choice, made at every meal, does most of what the stricter diets do without the restriction.