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How does eating too much fructose cause obesity?

How does eating too much fructose cause obesity?

In the United States, more than 40% of adults are obese, with approximately 10% having extreme obesity.

Obesity increases the chance of developing a variety of ailments, such as type 2 diabetes, heart disease, and several malignancies.

An energy imbalance between calories consumed and calories burned is the primary cause of obesity.

Obesity, however, may result from more than just calorie intake—it may also result from the calories.

According to recent studies, the simple sugar fructose, which is present in many foods, may be the cause of obesity and other related health issues.

Around 13% of persons globally, according to the World Health Organisation (WHO), are obese. Although obesity rates are rising in low-income nations, the majority are in wealthy nations.

According to National Institutes of Health (NIH) data, 42.4% of adults and 19.3% of children and adolescents in the United States were obese in 2017–18. Additionally, these figures are rising.

Obesity raises the risk of a number of illnesses. It is linked to a poor diet and an unbalanced energy intake, but it may also have a genetic component. These are listed by the NIH as follows:

What connection exists between fructose and obesity?

According to recent study, obesity may not just be caused by an energy imbalance; rather, the source of that energy may be what causes the illness.

According to the study, which was published in Philosophical Transactions of the Royal Society B, fructose may be the cause of obesity because of an evolutionary “survival switch” that makes people store energy from fructose rather than utilize it.

The study’s results were discussed by Dr. Eamon Laird, a postdoctoral research fellow at the University of Limerick in Ireland who was not engaged in the study, he observed:

This is a highly intriguing theory, even though it is only a narrative overview and not a systematic meta-analysis of the available data. It is conceivable that our present energy-dense diets have altered an evolutionary pathway that was advantageous millions of years ago.

Fructose converts to energy reserves.

According to the study, metabolic diseases like obesity may have arisen as a result of overstimulation of an evolutionary-based biological reaction called the “survival switch,” which is meant to safeguard animals before a crisis like hibernation.

Contrary to glucose, which is used as immediate fuel, the researchers contend that fructose causes the body to conserve energy.

This is better for an animal going into long-term hibernation than for a person who has constant access to high-sugar diets.

This “survival switch” may be more detrimental than beneficial in areas where people have easy access to food. People develop fat reserves as a result of the constant availability of high-fructose foods, which causes obesity and related health issues.

Metabolic effects of fructose

What causes fructose to make the body store energy rather than use it?

Adenosine triphosphate, or ATP, is often utilised and swiftly replaced from nutritional intake or fat storage. ATP is the chemical that supplies energy to power all cell operations.

Fructose, on the other hand, lowers the amount of ATP present in cells and hinders the production of ATP.

A chain of chemical processes that stop the mitochondria of the cell from making more ATP and put them under oxidative stress are triggered when ATP levels fall low enough.

Fructose consumption increases appetite in addition to lowering ATP levels. Once deposited as fat, these extra calories. The ATP levels eventually rise once more, but the fat reserves are still there.

Repeated exposure to oxidative stress causes mitochondrial dysfunction to become persistent over time. The body of a mammal that is hibernating adjusts to the low ATP levels by lowering the resting metabolic rate.

Without reducing calorie consumption, this lower energy usage leads to weight increase in persons who still have access to plenty of food.

Dr. Laird concurred that this theory could help to explain the rise in obesity.

He said, “I agree it could be one component. But obesity and metabolic syndrome are complex conditions; there is seldom just one contributing cause. Lack of exercise, unhealthy eating habits, vitamin deficiencies, socioeconomic causes, and even risk factors related to one’s race and ethnicity are all significant risk factors.”

Therefore, even if fructose did affect obesity, it would only have a minor impact overall, he continued.

Dietary sources of fructose

Although fruit naturally includes fructose, which gives it its sweetness, a normal Western diet also contains a variety of additional sources of fructose.

The majority comes from table sugar, high fructose corn syrup (HFCS), a sweetener manufactured from cornflour, and sucrose, a molecule composed of glucose and fructose chemically bound together.

Fructose can make up to 55% of HFCS. To transform the glucose in corn syrup into the sweeter-tasting fructose, manufacturers must add enzymes.

Since the fructose in HFCS is present as free molecules, it is absorbed more quickly than it is in table sugar.

HFCS is included in practically all processed foods and many other foods. They consist of:

  • sodas
  • fruit juices with added sugar
  • crackers
  • ready-made meals
  • salad dressings and condiments
  • a few pastries and bread.

According to the scientists, the growth in sugar consumption, particularly that found in processed foods, fructose-sweetened beverages, and carbohydrates with a high glycemic index (GI), is related to the global epidemics of obesity and diabetes.

Must you stay away from foods high in fructose?

Although he was not involved in the study, Dr. Mir Ali, a bariatric surgeon and medical director of the MemorialCare Surgical Weight Loss Centre at Orange Coast Medical Centre in Fountain Valley, California, stated that for people who are overweight or obese, “any source of sugar, including non-processed sugars, such as those found in fruits, can have a similar effect on the body.”

We advise our patients to minimize all sources of sugar, including fruits,” the doctor added.

However, Dr. Laird cautioned that most people should not worry excessively about fruit’s sugar content: Most of us don’t consume enough fruits, despite the fact that doing so would benefit our overall health by providing fibre, vitamins, and minerals. The modest amounts of fruit we do consume would probably not amount to much.

However, he continued, “The main risk probably arises when the fructose is highly concentrated and added to other foods (these foods often contain high fat, high sugar, and low nutrition), which could result in an increased risk of obesity.”

So maybe avoid that processed snack since it’s probably laden with fructose to help lower your risk of becoming obese.


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Could fructose contribute to development of Alzheimer?

Could fructose contribute to development of Alzheimer?

An increased risk of neurological disorders, such as Alzheimer’s disease, is connected with the shift in the global age demographic towards older ages. Dementia risk profiles may also be evolving. Over the past 50 years, the frequency of obesity and type 2 diabetes has increased, and these conditions have been linked to a higher risk of dementia.

Certain dietary modifications could potentially pose a direct danger. From an estimated 8.1 kg/person/year at the start of the XIX century to an estimated 65 kg/person/year today, there has been a diet change in the United States with regard to the consumption of refined sugar, notably high-fructose corn syrup (HFCS).

With an estimated 6 million people living with it, Alzheimer’s disease continues to be a serious health issue. The hypothesis that fructose, a prevalent sugar present in packaged foods and fruits worldwide, may contribute to the disease’s development has recently put forth in a narrative review.

Alzheimer’s disease is characterised by the production of aberrant beta-amyloid and tau protein clumps. Treatments aimed at these aberrant protein aggregates, however, have had mixed results.

Conversely, other scientists have suggested that changes in brain metabolism that take place before the formation of these protein aggregates may be to blame for the onset of Alzheimer’s.

According to studies, diets that cause the body to produce a lot of fructose or foods that contain a lot of fructose might cause metabolic problems like obesity, diabetes, and high blood pressure.

Fructose survival pathway

A glucose and a fructose molecule make up each mole of table sugar, also known as sucrose. Most cell types and tissues in the body use glucose as fuel.

Despite the fact that fructose can be used as energy, the body prefers to store it as fat or as the storage carbohydrate glycogen.

The authors’ theory states that an animal can survive for extended periods of time without food or water by activating a survival response when it consumes fructose in excess. During migration or hibernation, the animal may be able to survive thanks to this survival reaction.

Consuming fructose results in an increase in thirst and hunger instead of fullness, which is produced by consuming glucose. Animals’ urge to forage is thereby stimulated by fructose ingestion. The fructose survival pathway, in particular, entails saving energy for just required actions, such as foraging, and minimising energy expenditure for body processes at rest.

Reducing the sensitivity of tissues to insulin, such as muscles, leads to a decrease in glucose absorption and consumption, which lowers energy expenditure. Moreover, the liver stores extra energy in the form of fat and glycogen.

The main mediators of the survival response include fructose, uric acid, and vasopressin. When this fructose survival route is activated for an extended period of time, the metabolism is disrupted, mimicking a number of the symptoms of metabolic syndrome.

They include persistent low-level inflammation, insulin resistance, high blood pressure, and weight gain. The fructose survival pathway can potentially affect the metabolism of the brain.

Impact on the brain

While making up only 2% of the overall mass of the body, the human brain consumes almost 20% of the total energy used while at rest. Furthermore, glucose is the only fuel that can be used by neurons, which make up the majority of brain cells.

The fructose survival pathway alters the metabolism of the brain at the regional level while reducing energy expenditure to conserve glucose for the brain.

In particular, the scientists believe that activating the fructose survival pathway causes the brain’s food-seeking areas to become active. An increase in impulsive and exploratory actions that enable the animal to quickly investigate risky locations promotes this foraging response.

Meanwhile, the foraging response is linked to the inhibition of brain regions, such as those involved in logic, memory, and impulse control, that may decrease foraging activity.

In other words, the aforementioned brain areas involved in cognitive function experience a drop in energy metabolism when the foraging response is activated.

Evidence supporting the role of fructose

The rise in fructose levels in the brain, according to the researchers’ theory, may play a role in the onset of Alzheimer’s disease.

Nevertheless, given that individual fruits only contain a modest amount of fructose and that only 1% to 2% of ingested fructose reaches the brain, this rise is most certainly not attributable to fruit consumption as a whole.

However, it appears that ingestion of foods high in glucose, glycemic index, and salt may be more relevant in raising fructose levels in the brain.

The levels of fructose in the brain could therefore be increased by a diet heavy in salt and carbohydrates. Moreover, the uric acid that is created when fructose breaks down in the periphery can encourage the creation of fructose in the brain.

According to studies, consuming more high-fructose corn syrup or table sugar, foods with a high glycemic index, and salty foods is linked to a higher risk of Alzheimer’s disease.

In line with this, metabolic diseases linked to increased consumption of certain foods, such as obesity, insulin resistance, and diabetes, are also risk factors for Alzheimer’s disease.

The fructose metabolism

According to Dr. Johnson, treating fructose metabolism may be essential for the management or prevention of Alzheimer’s.

The majority of the evidence, he continued, “suggests three characteristic findings in early Alzheimer’s that seem to precede the end-stage presentation: these are the presence of insulin resistance associated with reduced glucose uptake in the brain, the fact that there is mitochondrial dysfunction in the brain, and that there is local inflammation, or “neuroinflammation,” in the brain.

Others are still attempting to cure this condition by administering intranasal insulin or by reducing inflammation. Yet once more, this only addresses the symptoms and not the root problem, according to Dr. Johnson.

Moreover, the metabolism of fructose raises the amounts of uric acid in the brain, which on its own can cause inflammation and memory problems. For instance, memory impairments and hippocampal inflammation are seen in hyperuricemic rats that produce too much uric acid.



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