Diet drinks and foods that contain sucralose, a widely used sugar substitute popularly known as Splenda, may actually increase your appetite and cravings, a new study found.
“Our findings suggest that sucralose may create a mismatch in the brain: It provides a sweet taste but lacks the expected caloric energy,” says corresponding author, Kathleen Alanna Page, MD, director of the USC Diabetes and Obesity Research Institute and co-chief of the division of endocrinology and diabetes at the Keck School of Medicine of USC in Los Angeles.
In other words, if your body is expecting a calorie because of the sweetness, but doesn’t get the calorie it’s expecting, that could trigger cravings and increase appetite, says Dr. Page.
Do Sugar Substitutes Help With Weight Loss?
Sugar substitutes like sucralose, used in drinks including sugar-free Red Bull, are a popular choice for people trying to cut calories or reduce their sugar intake. It’s estimated that about 40 percent of Americans eat and drink them.
But there’s a growing body of evidence that suggests replacing foods and drinks containing real sugar with ones containing sugar substitutes doesn’t help with weight loss and may even cause people to gain weight.
How Sugar Substitutes Affect the Brain
Researchers set out to try to find out what happens in the body and brain to explain how zero calories may end up adding to weight gain rather than subtracting, and if the effects are the same on men versus women and people of different sizes.
Earlier research that’s been mostly done with animal models and large population studies has hinted at a link between calorie-free sweeteners and obesity, but has not directly shown how they might impact hunger in humans.
The study included 75 participants between 18 and 35 years old. They were roughly evenly split between male and female and weight status (healthy weight, overweight, or obese).
On three separate visits, each participant drank 10 ounces of one of the following:
- A sugar-sweetened drink
- A matched-sweetness drink made with sucralose
- Water
This allowed the researchers to look for differences both within and between each person. At each visit, researchers collected brain scans and blood samples, and participants rated how hungry they were both before and after consuming the drink.
Sucralose increased brain activity in the hypothalamus and increased feelings of hunger compared with drinking sugar. Sucralose also increased brain activity compared with water, but people felt the same amount of hunger.
The researchers also used MRI scans to study functional connectivity, which shows how regions of the brain communicate with one another.
Sucralose led to increased connectivity between the hypothalamus and several brain areas involved with motivation and sensory processing — including the anterior cingulate cortex, which plays a role in decision-making.
This mismatch may alter how the brain processes sweet taste and metabolic signals, which could impact cravings and eating behavior, says Page.
The MRIs showed sex-related differences in response to sucralose: Female participants showed greater changes in brain activity than male participants did.
“And the impact of sucralose on the hypothalamus was strongest in individuals with obesity,” says Page.
How Your Hormones Respond to Artificial Sweeteners
Scientists also looked at how sugar and sucralose affected hormones tied to hunger.
As expected, the sugar drink led to increases in blood sugar and the hormones that regulate it, including insulin and glucagon-like peptide 1 (GLP-1). “The body uses these hormones to tell the brain you’ve consumed calories, in order to decrease hunger,” Pageshe says.
Drinking sucralose, on the other hand, had no effect on those hormones, leading hunger and cravings to continue.
Artificial Sweeteners May Not Support Weight Loss in the Long Run
“I like the explanation that the authors propose, that sucralose increases blood flow from the hypothalamus to areas of the brain involved in stimulation and hunger,” says Dr. Spratt.
Should You Kick Your Diet Soda Habit?
Artificial sweeteners can be a useful alternative to sugar for people with diabetes, Spratt says. But otherwise, she recommends avoiding sugar substitutes.
If you’re hooked on diet soda, she says, “Natural alternatives like water and unsweetened tea or coffee are the best options,” says Spratt.
Sparkling water is also an option, though it’s unclear what impact, if any, artificially flavored water would have on the hypothalamus, she says.
“But you could flavor your tea or water with a slice of actual lemon or lime or with mint leaves. One of the things I love to do is infuse my water with fruits and vegetables. My favorite combination is pineapple and rosemary,” says Spratt.