Type 2 diabetes: How do fructose-sweetened drinks affect risk?

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A new study shows that sugary drinks that contain fructose raise the risk of type 2 diabetes more than other fructose-containing foods.

New research finds that ‘nutrient-poor’ sweetened drinks have a harmful effect on metabolic health when they add excess energy.

A range of recent studies has pointed out the potential health risks of sugary drinks. Studies have confirmed that there is a link between sugary drinks and obesity, as well as cautioning that as few as two sugary drinks per week may raise the risk of type 2 diabetes considerably.

Now, a comprehensive review of existing research confirms that fructose-containing drinks can increase the risk of type 2 diabetes more than other foods that contain fructose.

Although some research has suggested that fructose might be a good alternative to sugar, especially for people who are already living with diabetes, more recent studies have pointed out that “fructose could be particularly detrimental to metabolic health, and even more so than other sugars.”

As the researchers explain, fructose is a natural ingredient in several foods, such as fruits, natural fruit juice, honey, and even some vegetables. However, some food manufacturers artificially add the compound to soft drinks, desserts, cereals, and other baked foods.

Foods with fructose and metabolic health

To find out, the researchers analyzed the conclusions of 155 studies that looked at how different food sources affected peoples’ blood sugar levels. The researchers followed the participants, some of whom had diabetes, for up to 3 months.

During this time, the researchers also assessed the participants’ glycated hemoglobin — that is the amount of sugar that is attached to red blood cells — as well as their glucose and insulin levels after a period of fasting.

Researchers divided the 155 controlled intervention studies into four groups based on their design.

  • Substitution studies compared the energy derived from sugars with that from other carbohydrates.
  • Subtraction studies removed sugar-derived energy from the participants’ diet and compared it with a regular diet.
  • Addition studies added glucose-derived energy to the diet and compared it with a non-sugar-enhanced diet.
  • Ad libitum studies replaced the energy from sugars with other nutrients that the participants were free to consume at will.

The reviewers assessed the bias and the level of certainty of these studies.

Sweetened drinks vs. other sugary foods

Overall, the review found that most of the fructose-containing sugary foods do not harm blood sugar levels when they do not add excess calories. Some of the studies, however, found a harmful effect on fasting insulin levels.

In fact, fruit and fruit juice, which are high in fructose, may even benefit the blood sugar and insulin levels of those with diabetes, when these foods do not add excess calories, the review suggests.

However, some “nutrient-poor” foods that add excessive energy to the diet, such as sweetened drinks and fruit juice, have a harmful metabolic effect.

The researchers hypothesize that the higher content of fiber in fruit, for example, may partly explain this difference, because they slow down the release of glucose. Also, fructose has a lower glycemic index than other carbohydrates.

“These findings might help guide recommendations on important food sources of fructose in the prevention and management of diabetes,” says the study’s lead author.

“But the level of evidence is low,” he cautions, “and more high-quality studies are needed.” 

Until more information is available, public health professionals should be aware that harmful effects of fructose sugars on blood glucose seem to be mediated by energy and food source.

Why a low-carb diet can help you lose weight and keep it off

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“The largest and longest feeding study to test the ‘carbohydrate-insulin model, concludes that a lower carb intake burns more calories, which may help people maintain weight loss over a longer period of time.

Eating a high-quality, low-carb diet may help us stave off weight gain for longer.

when we lose weight, the body adapts by lowering its energy expenditure. In other words, it burns fewer calories.

This way, the metabolism protects itself against long-term weight changes.

However, when the weight loss is intentional, this adaptive response can be frustrating for dieters, as it leads to weight regain.

Although weight gain after dieting is a well-known phenomenon, researchers do not know much about how different diets affect the way the metabolism responds to them.

The so-called carbohydrate-insulin model, however, suggests one such mechanism. It posits that highly processed foods high in sugar drive hormonal changes that increase the appetite and lead to weight gain.

“According to this model, the processed carbohydrates that flooded our diets during the low-fat era have raised insulin levels, driving fat cells to store excessive calories. With fewer calories available to the rest of the body, hunger increases and metabolism slows — a recipe for weight gain.”

In this context, we decided to investigate the effects that different diets had on the metabolism. Specifically, we looked at the carb-to-fat ratio in varying diets over a 20-week period.

Studying carb intake, weight, and calories

The researchers examined the effect of different diets on 234 adults aged 18–65 whose body mass index (BMI) was at least 25. As part of the study, the participants had also adhered to a weight loss plan for 10 weeks.

By the end of the trial, 164 participants had achieved their weight loss goal of around 12 percent of their total weight. Then, they adhered to either a high-, moderate-, or low-carb diet for 20 weeks, allowing the researchers to examine if they managed to maintain the weight loss.

The high-carb diet was composed of 60 percent high-quality carbs, the moderate-carb one had 40 percent carbs, and the low-carb diet had 20 percent carbs. The diets also minimized sugar intake and used whole grains.

During this time, the scientists measured the participants’ weight and tracked the number of calories they burned. They also examined the participants’ insulin secretion and metabolic hormones.

‘A 20-pound weight loss after 3 years’

At the end of the study period, people in the low-carb group burned significantly more calories than those who had been on a high-carb diet.

Specifically, participants who were on a low-carb diet burned around 250 kilocalories more per day than those who were on a high-carb diet.

“If this difference persists — and we saw no drop-off during the 20 weeks of our study — the effect would translate into about a 20-pound weight loss after 3 years, with no change in calorie intake.”

The results also indicated that for participants who had the highest insulin secretion, the impact of a low-carb diet was even more significant: low-carb dieters burned 400 calories more per day than high-carb dieters.

“A low glycemic load, high-fat diet,” explain the authors, “might facilitate weight loss maintenance beyond the conventional focus on restricting energy intake and encouraging physical activity.”

 “Our observations challenge the belief that all calories are the same to the body.”

“This is the largest and longest feeding study to test the ‘carbohydrate-insulin model,’ which provides a new way to think about and treat obesity.”