Could artificial sweeteners actually cause weight gain?

DEAR DOCTOR K:

For 20 years, I’ve substituted artificial sweeteners for sugar in my coffee, and switched to diet soft drinks to avoid obesity and the diseases that overweight people are prone to, like Type 2 diabetes. Now I hear that new research says that’s a bad idea. What is going on?

DEAR READER:

Here’s what’s not confusing: More than a modest amount of sugar each day is not good for you. Nothing’s changed there. The sweet tooth that many of us have (I plead guilty) leads us to eat too much sugar.

Sugar contains easily absorbed calories. That makes it harder to maintain or achieve a healthy weight. It also increases our risk of developing Type 2 diabetes, the most common form of diabetes. Sugar-sweetened soft drinks and fruit juices are particularly bad actors.

The development of no-calorie artificial sweeteners, like saccharine, sucralose and aspartame, seemed like a godsend. Like you, I switched from regular drinks to “diet” drinks a long time ago. Artificial sweeteners taste as sweet as (or sweeter than) sugar, but contain virtually no calories. What’s not to like?

In previous columns, I’ve said that there was some evidence that consuming artificial sweeteners might increase our appetite for sugar-containing sweets. That is definitely not a good thing, if true. I still regard it as unproven.

But recently, a scientific study was published in a prestigious scientific journal, Nature, that set me back on my heels. If other scientists confirm this work, it has important implications for all of us. To tell you what the study showed, I first need to explain a little biology.

Many foods contain carbohydrates (“carbs”). Carbohydrates resemble a chain with multiple links. When they enter our gut, the links in the chain are separated by digestion. Table sugar is a simple chain: just two links, easily separated. It’s the single links that mainly are absorbed into our blood. The most common is called glucose. When your doctor measures your blood sugar, glucose is what is being measured.

Any food, say a slice of an orange, contains calories. But those calories add to our weight, and influence whether we might develop diabetes, only if they are efficiently broken down into single links — glucose — and then are absorbed into our body.

Our intestines contain trillions of bacteria of different types. Some types are very good at breaking up carbohydrates into glucose; other types are not. If you’re a person with lots of the first type of bacteria living inside you, every slice of orange you eat will lead to more calories getting into your blood.

The recent study presents evidence indicating that artificial sweeteners may encourage the growth of the types of bacteria that generate more glucose — and, hence, lead us to absorb more calories. In other words, while the sweeteners don’t contain calories, they may cause us to absorb more calories.

If other scientific studies confirm these findings, I will be further lowering my modest consumption of artificial sweeteners. I’ll keep you posted.