It has long been known that eating a diet high in sugar and fats increases the risk of obesity, due to the excess calories and energy dumps.
But now researchers believe that the most popular sugar in American foods causes biological changes in the human body, making it physically easier to get fat and harder to lose weight.
High fructose corn syrup is used in numerous food products in the U.S., even those considered healthy, including protein bars, whole wheat bread and breakfast cereals.
A new analysis of previous studies has found that it lowers levels of fullness hormone, prevents the body from using fat stores for energy and slows metabolism, making it harder for the body to burn energy from food.
The findings challenge the long-held belief that the sole dictator of obesity eats too much and consumes little energy, leading to an accumulation of fat in the body.
Fructose occurs naturally in fruits, but the type most commonly consumed in the U.S. is extracted from corn, stripped of essential nutrients and fiber and converted into high fructose corn syrup.
High fructose corn syrup is very common in popular foods because a small amount is incredibly sweet, making it cost-effective for food manufacturers. This ingredient has been identified as one of the leading causes of obesity
The fructose in fruit affects the body differently than the type of ultra-sweet fructose found in highly processed and often the most appealing foods
It is found in thousands of everyday food products, from bread and protein bars to sweets, and has long been linked to diabetes, high blood pressure and heart disease.
Now scientists have discovered that refined high fructose syrup has multiple effects on the body, making it more likely to lead to obesity than other types of sugar and food additives.
They said: ‘Although virtually all hypotheses recognize the importance of reducing ultra-processed and ‘junk’ foods, it remains unclear whether the focus should be on reducing sugar intake.’
Subsidies help keep prices low, making it cost-effective for food manufacturers to make highly processed foods that contribute to the U.S.’s rising obesity rates, which are higher than those of other rich countries.
High fructose corn syrup is made from corn and broken down into a type of sugar called glucose. Some of that glucose is then converted into super sweet fructose.
Much of the research scientists drew from was conducted on mice, a limiting factor when it comes to determining how these hypotheses might apply to humans.
Challenging the age-old view that obesity is caused by overeating and little exercise, the researchers looked at additional hypotheses presented by other researchers in various studies to search for the cause of obesity.
They found that all hypotheses are valid, including one that blames simple carbohydrates that are quickly broken down in the body for stimulating insulin production, which leads to the build-up of fat.
Dr. Richard Johnson, lead researcher from the University of Colorado Anschutz Medical Campus, said: ‘Essentially, these theories, which place a litany of metabolic and nutritional factors at the heart of the obesity epidemic, are all pieces of a puzzle united by one final piece: fructose .
‘Fructose causes our metabolism to go into an energy-saving mode and loses our control over appetite, but fatty foods become the main source of calories that cause weight gain.’
Fructose is found in fruit, but scientists say a regular apple or banana for breakfast won’t pose a problem. In fruit, the fructose is balanced by the high content of healthy fiber and other nutrients.
The experts explained that when people eat foods high in fructose, the amount of usable energy available to support the body’s cells plummets, leading to feelings of hunger.
Most of the carbohydrates and fats that people eat replace levels of ATP, a molecule that fuels cells so they can move, divide and perform basic functions in the human body necessary for survival.
This causes the release of a hormone called leptin, which signals to the brain that it is time to stop eating.
But when fructose is metabolized in the liver, it uses ATP as an energy source. This causes fuel levels to drop while disrupting the body’s ability to use stored fat for energy.
The reduction of ATP in cells is associated with hunger, thirst, increased food intake, decreased resting metabolism, increased salt intake and more, all of which can lead to weight gain.
Meanwhile, the liver, where fructose is metabolized, produces insulin, which lowers blood sugar levels, leading to feelings of hunger.
In 2022, a record three states classified more than 40 percent of their adults as obese — West Virginia, Louisiana and Oklahoma — and 19 states had rates above 35 percent.
Research into specific causes of obesity, down to the nutrient, has major implications for the broader fight against obesity, providing insight into potential targeted treatments that could ultimately prove even more effective than the most effective drugs on the market, Wegovy and Ozempic.
The fructose theory rounds out all the other theories thought to promote weight gain – eating highly processed foods and then doing nothing to burn that energy – as well as eating too many high-carb foods that are quickly broken down in the body and reduce muscle mass to increase. blood glucose levels, leading to hunger and cravings for more junk food.
Dr. Johnson said: ‘Fructose is what causes our metabolism to go into an energy-saving mode and lose our control over appetite, but fatty foods become the main source of calories that cause weight gain.’
The researchers wrote: ‘As you can see, all hypotheses tend to focus on the role of highly processed ‘junk’ foods, but each hypothesis focuses on a different food group, and this has led to different approaches to management .
‘It has often been assumed that these hypotheses are incompatible with each other… But here we would like to propose that all of these hypotheses focus on important aspects of the way obesity and diabetes develop, and that they are not incompatible, but actually complementary.’
They compared their theory to the preparation of bears for hibernation.
The animals eat fruit to maintain their fat reserves and thus survive for eight months.
The researchers added: ‘In fact, these responses are intended to aid survival prior to a crisis by stimulating the desire and search for food and water, by encouraging excessive food intake, by enabling foraging but reducing the reduce energy requirements while resting… by stimulating fat. production while blocking fat burning.
‘It is a spectacular system that prepares animals for a time when food, water or oxygen are less plentiful, such as in preparation for long-distance migration or hibernation.’
The findings were published in the journal Obesity.