Artificial sweeteners linked to weight gain over time, review of studies says

— -- Consuming too much sugar, we know, is linked to obesity, high blood pressure and diabetes. And people who are watching their weight may choose artificial sweeteners to fight back — products like aspartame, sucralose and steviocide (brand names: Equal, Splenda and Stevia, respectively).

But a new analysis of studies in The Canadian Medical Association Journal looked at the long-term heart health, weight, stroke incidence and blood pressure levels of more than 406,000 people who said they use artificial sweeteners in place of sugar and found that the effects weren't on the positive side.

"We found that consumption of nonnutritive sweeteners was associated with modest long-term weight gain in observational studies," the study authors found. "Our results also extend previous meta-analyses that showed higher risks of Type 2 diabetes and hypertension with regular consumption."

The 30 studies that they reviewed followed groups of people using artificial sweeteners — such as aspartame, sucralose and steviocide — and included longer, larger studies with follow-ups every four to nine years. The researchers found that people who routinely used artificial sweeteners gained weight and had higher risks of obesity, high blood pressure and stroke.

Over 10 years, increases in weight and body mass index, or BMI, were modest.

Those those looking for weight loss help in the short term did not appear to benefit either. People in the seven shorter randomized, controlled studies reviewed in the analysis did not show any consistent weight loss after six months.

ABC News' chief women's health correspondent, Dr. Jennifer Ashton, explained that any sweetener can trigger the same response from the brain, which could contribute to the long-term issues found in this study.

"We know from things called functional MRIs that in the brain — whether its good old table sugar or honey or agave or anything with a chemical name — it lights up that reward center, and what does that do?" she said today on "GMA." "It makes us eat more, want more, and we get into that vicious cycle."

The study strongly highlighted the association of artificial sweeteners and increasing waistlines along with other cardiometabolic effects but not a direct causation. In other words, it could be something linked to using artificial sweeteners that makes the weight gain happen, like a change in overall eating habits.

And as in other nutrition-based studies, the participants reported what they ate. That means it's not a perfect reflection of what they consumed, and the duration of the study was limited, which may not properly capture chronic dietary exposure.

Ashton recommends that people with a sweet tooth reduce their sugar intake and do it slowly.

"Let's say you put two teaspoons of something in your coffee, go to one, go to half, slowly taper down," she said. "A good reminder: maximum 25 grams a day for women of added sugar. For men, it's about 37."

Based on the data from the studies, she said, one thing that clearly works for weight loss is portion control.

"Portion control works. Diets in general — lean protein, high fruits, vegetables, watching the sugar — those work," Ashton said.

In other words, diet sodas and artificial sweeteners may not lower your weight and improve health, and overall diet is more important.