How Diet Sodas Wreck Your Diet

I was waiting to check out at the grocery store recently. Ahead of me in line was a couple in their 30s with their two children, who looked to be about 8 and 10. The children were both overweight—what used to be called “pudgy.” But Mom and Dad were big. Really big.

I’m interested in health—and I’m a little nosy—so I took a peek into their cart. Fresh and frozen vegetables, some chicken and fish, a carton of eggs. So far no problem. But there at the back of the basket were about ten two-liter bottles of diet soda. Aha! There was the culprit.

It seems so simple, right? We gain weight when we take in more calories than we burn. We lose weight when we take in fewer calories. So if we eat foods that contain fewer calories than the regular kind—their “diet” cousins—we should be able to lose weight easily.

Not so fast.

It’s Not Nice to Fool Mother Nature

Food makers know what you want. They know you want foods that taste good, that feel right in your mouth, that satisfy you. So when the high-calorie ingredients go away, something else replaces them. When sugar goes away, aspartame or sucralose appears. When fat leaves, starches and thickeners arrive. When carbs get cut, other calorie-loaded ingredients replace them.

Low-fat and low-carb foods have their own problems. But sugar-free foods are the sneakiest. Here’s how diet sodas wreck your best efforts at weight loss.

  • When you drink a diet soda, your mouth tastes the sweetness.
  • Your pancreas releases more of the hormone insulin, to get ready for the sugar it thinks is on the way. (That’s called the “cephalic phase insulin response,” by the way.)
  • There is no sugar on the way, of course. The extra insulin works on the sugar that’s already in your bloodstream.
  • Your blood sugar level drops.
  • Low blood sugar triggers the signal for hunger.
  • You feel hungry, so you eat something.

Total calorie intake can end up being greater than if you’d had a regular drink instead of the diet soda.

There are a few competing theories about why sugar substitutes sabotage your weight loss efforts. Some think that the fake sugar affects the way you digest real sugar. Others believe that the sugar substitute affects the bacteria in your gut. No matter what the cause, when you drink a diet soda you end up eating more.

Want Proof About Sugar Substitutes?

I’ve always had the feeling that fake foods are bad for us. The facts keep piling up. Let’s look at some studies about the weight effects of diet drinks.

A study in San Antonio followed more than 5,000 adults for nine years. People who drank three or more diet sodas a day increased their risk of becoming overweight or obese by 93%. Those who were already overweight bumped their risk of becoming obese by 103%. (Here overweight means a body mass index, or BMI, of more than 25. Obese means a BMI of more than 30.)

The famous Framingham Heart Study has followed people since 1948. People in that study who drank more than one regular soda daily had a 48% increased risk of developing metabolic syndrome. No surprise here. But those who drank more than one diet soda daily had an 80% increased risk! (Metabolic syndrome is a combination of large waist size and high blood pressure, blood sugar, cholesterol, and triglycerides.)

I could go on—and on—but you get the idea.

What Do I Do Instead of Diet Soda?

So here’s what I want you to do. If you’re currently drinking diet sodas, stop. It’s that simple. It may not be easy, but it is simple. Here are some suggestions on how to get yourself off these waist-busters. You may have heard some of them before. They’re still valid, though.

Drink water. If you don’t like the taste of your local water, I understand. I’ve been places where the local water tasted of sulfur, or minerals, or metal. But even the most basic water filter will get rid of that taste. Try a pitcher filter like a Brita or Pur. They’re around $20 each.

Want something fizzy? Replace your diet soda with club soda plus fruit juice. (Watch out for fruit “drinks,” though. Many are packed with added sugar.) My wife adds a squirt of lemon juice to her water. It’s no excuse that you need the caffeine from the soda—but that’s a topic for another time.

Go for a short walk. If you’re truly thirsty, of course you want to drink something. But if it’s really a craving, then a little exercise will head it off. You don’t have to break a sweat. A walk around the block will do.

Watching your weight makes sense. People who weigh more have more problems with their joints, their eyes, and their heart, along with an increased risk for diabetes and cancer. Just don’t give in to the myth that diet foods are the answer.