A newly released study says the type of sugar you eat may affect your cravings for high-calorie foods.

Fructose vs Glucose

Fructose in fruit causes people to still be hungry and crave food after eating fruit

• Glucose: sugar found in carbs
• Fructose: sugar found in fruits, honey and corn
• Compared consuming glucose to consuming fructose among 24 healthy volunteers
• Drank 10-ounce glass of cherry-flavored liquid w/ 2.5 ounces of fructose or glucose
• Took blood samples to measure levels of: glucose, fructose, insulin, leptin and ghrelin (enzymes involved in controlling hunger and feelings of fullness)

Before having drinks, participants were ask to rate their desire to eat on scale 1-10 from “not at all” to “very much.”

Drank liquids and had MRI brain scans while looking at images of food and neutral objects (i.e. buildings), while rating hunger using scale. They were then presented with images of high-calorie foods and asked if they wanted food now, or a monetary award a month later. 

The results of the study were as follows:

Compared to consuming glucose, consuming fructose led to:

• Greater responses to food cues in the orbital frontal cortex of the brain (region that plays an important role in reward processing)
• Increased responses to images of food (suggests increased craving compared with glucose)
• More likely to choose high-calorie food over future monetary reward
• No difference in leptin or ghrelin levels between fructose and glucose drinkers.
• Plasma insulin response was much lower in fructose drinkers (may affect what we eat)

Comparing the effect on our bodies:

• Glucose – starchy carbs like potatoes
• Fructose - majority of fruits and vegetables

Our bodies produce glucose, but not fructose. Both have same caloric value, but are metabolized very differently by the body.

When we consume glucose insulin is released. Pancreas secretes insulin, and insulin drives glucose into cells to be used for energy. Also sends signal to brain saying ‘you’ve eaten.’

When we consume fructose, it doesn’t stimulate insulin secretion, and if there’s no insulin, you don’t get signal that you’re full. Every cell in the body can use glucose, but the liver is the only organ that can metabolize fructose in significant amounts. When people eat a diet high in calories and high in fructose, liver gets overloaded and starts turning the fructose into fat.

Should we avoid eating fruit since it contains fructose?

No - people should not stop eating fruit.. It has a relatively low amount of sugar compared to processed foods, soft drinks

• An orange - about 5g of sugar
• 12-ounce can of soda - about 25g of sugar
• Packed with fiber - helps slow down absorption of food and makes you feel full
• What people should limit - fructose in the form of added sugars (fructose is used in many modern sweeteners)
  • i.e. high-fructose corn syrup – found in sodas, desserts, cereal, etc.
  • Cheaper than sucrose, gives products longer shelf life

Studies show it contributes to obesity, heart disease, high blood pressure, liver disease, type 2 diabetes, cancer. Researchers recommend lowering fructose consumption to around 15g per day.