TOFI: the health threat of fructose

Meyken Houppermans, PhD. CrossFit Level 3 Trainer.
Head Coach and Founder
TOFI: Thin on the outside, fat on the inside. These people have a normal Body Mass Index and waist size, but at higher risk of health problems than some obese people. Appearance is not everything. A Western diet, and high intake of fructose (Fruit), is a problem. In this article we explain the negative affects of fructose; why it is not about how much you eat but what you eat, and what dietary changes can improve your health.

Metabolic Obese Normal Weight (MONW)

In the United States, 30% of all adults are obese and 70% are not. In The Netherlands, half of all adults are overweight and almost 15% are obese. Of those 30% obese Americans, 80% are sick. They suffer from metabolic dysfunctions such as type 2 diabetes, high cholesterol, high blood pressure, cardiovascular problems, cancer, and dementia. This means that 20% of all obese people are healthy despite being seriously overweight. Fit and fat. It is striking that of the remaining 70% not- obese Americans about 40% also have metabolic dysfunctions. Not fat and unfit. They are MONW: metabolic obese normal weight.[1] Sometimes also known as Skinny Fats: people who have a healthy body weight, exercise regularly especially cardio exercise, and follow a calorie- restricted diet.

This indicates that weight, Body Mass Index (BMI), waist circumference, or appearance are not good stand-alone indicators for health. This also indicates that not just the fat that is visible on the outside need attention, but moreover the underlying causes of metabolic dysfunctions in people with a high as well as with a normal Body Mass Index.

Visceral fat and non- alcoholic fatty liver

Metabolic dysfunctions that occur in people with a normal BMI are often associated with high visceral fat (abdominal fat) and non-alcoholic fatty liver.

Visceral fat surrounding vital organs is an important risk factor for chronic diseases such as diabetes, depression, dementia, and cardiovascular disease. An unhealthy lifestyle with over-consumption of processed food and little exercise are important causes of visceral fat. A large waist circumference is indicative for visceral fat, but a small waist circumference does not rule out a high level of visceral fat.

Non-alcoholic fatty liver is a condition that involves an excessive supply of fatty acids to the liver. The liver is unable to process these fatty acids and can store only small amount of fat, about 5% of the weight of the liver. When more fat is stored in the liver, we speak of fatty liver. This is a reversible process: the fat accumulation disappears when the cause is removed.[2]

A disturbed sugar metabolism is one of the causes of fatty liver. The sugar metabolism is disrupted by an insensitivity to insulin. After eating sugar, the blood sugar level rises. Insulin ensures that the sugars in the blood are absorbed into our body cells after which the blood sugar level drops. By eating a lot of sugars, the blood sugar level rises, after which insulin lowers it again. Due to large fluctuations in blood sugar levels, our body can become insensitive to insulin (insulin resistance). The blood sugar level then remains high. To compensate, the pancreas produces more and more insulin. This ultimately leads to type 2 diabetes. Excess sugars are converted into fats in the liver. These fats are stored in the liver, causing fatty liver.[3]

In The Netherlands, about 25% of all adults suffer from non-alcoholic fatty liver disease, and 90% of all Dutch people with obesity have fatty liver disease.[4] Visceral fat and fatty liver disease are mostly caused by a Western diet and a high intake of fructose.[5]

Western diet

A Western diet is characterized by chronic overconsumption of calory rich food; a high intake of refined sugar, salt, and saturated fat; and especially a high intake of fructose. This dietary pattern is associated with metabolic dysfunctions, fatty liver, disruptions of the immune system; increased rates of cancer; increased risk of allergic and auto- inflammatory disease; and chronic metabolic inflammation. This is inflammation of tissue in body fat, skeletal muscle, liver, pancreas, intestine and in the brain, often seen in obesity. Because a Western diet can negatively impact our genes, the consequences of unhealthy food choices today are passed on to the next generation.[6]

Fructose, the culprit of health problems

As mentioned above, about 25% of all Dutch adults suffer from non-alcoholic fatty liver disease and 90% of all Dutch people with obesity have fatty liver disease. This is mainly a result of an excessive intake of fructose. [7] In addition, the Dutch eat too much salt and fat and too little dietary fiber. [8] (Weight loss by eating fiber)The daily intake of sugars (mono- and disaccharides*) including of fructose is on average 110 grams. [9]

*Monosaccharides are fructose, galactose and glucose. The body can absorb these directly. Disaccharides are lactose, maltose, sucrose (beet or cane sugar) and trehalose. Lactose is broken down by the body into glucose and galactose. Sucrose is broken down into glucose and fructose. Maltose and trehalose are broken down into glucose. Table sugar consists of half glucose and half fructose [10]

The advised daily intake by the World Health Organization is approximately 50 grams of ‘free’ sugar per day for an adult. Free sugar is sugar added to the product by the manufacturer plus all ‘natural’ sugar from honey, syrup, fruit juices and fruit concentrates. Sugar naturally present in fresh fruit, vegetables and not- sweetened or flavored dairy products is not considered free sugar.[11]

A very small part of the sugar we eat is directly used by the body as energy, for example during a marathon. A limited amount is stored as glucose in the liver and muscles, about 300 to 400 grams. That is equal to 1200 to 1600 kcal. The rest is not used but converted into fat.

Fructose is fruit sugar. It is sweeter than glucose, and therefor food producers need less to sweeten a product. The uptake of fructose by the body takes twice as long as the uptake of glucose. Although that might seem appealing to people with diabetes, and fruit sugar might have a positive connotation, the negative health effects of a high intake of fructose are serious. [12]

Products high in fructose are (dried) fruit, honey and agave syrup, fruit juices, soda, pastries, candy, flavored yoghurts, sauces such as ketchup, and most processed foods. Fructose is not always mentioned by its name on a food label, and are therefor not easy to recognize. Fructose can also be registered as monosaccharide; high fructose corn syrup (in Dutch: glucosefructosesiroop); fruit sugar, l(a)evulose and most ingredients ending with …ose [13]

Health problems can be the result of a high intake of fructose. An intake of more than 100 grams per day is considered high. To give you an idea: One apple contains approximately 8 grams of fructose, one tablespoon of honey about 10 grams, one date 7 grams, one cup of raisons 43 grams, and one zucchini 8 grams.

A high intake of fructose can cause disruptions of fat- and sugar metabolism, as described above in relation to non-alcoholic fattyliver. Additionally, compared to glucose, a high intake of fructose causes visceral fat accumulation, related to chronic diseases.

Furthermore, a high intake of fructose causes inflammation in body cells that metabolize it quickly. As a result, the production of cortisol* increases to counteract these inflammations. High fructose intake also stimulates the brain to produce cortisol. A prolonged rise in cortisol is associated with an increase in visceral fat and fatty liver. This explains why getting fat on the inside can happen without having to be overweight by eating too much calories.[14]

Also, fructose promotes the formation of reactive oxygen species, which leads to cellular dysfunction and aging, and promotes changes in the brain's reward system, which drives excessive consumption and addiction-like behavior. And fructose can cause intestinal problems such as diarrhea, stomachache and bloated-ness[15]

*Cortisol is a hormone produced by the adrenal cortex in the body. It has an important function in protecting the body from the effectsof physical and mental stress. [16]  An acute rise in thecortisol level ensures that we can take action in case of an emergency.Cortisol suppresses the immune system and stimulates the storage of memories inthe brain. However, a long-term high cortisol level, such as during a burnout,causes loss of muscle strength, a disturbed fat distribution (an increase invisceral fat) and mental problems such as depression and irreparable damage to brain cells and memory. [17]

Same calories, more weight gain

Obesity is often related to a caloric imbalance. Consuming more calories than burned causes excess body fat. But as we described above, a high intake of fructose can lead to metabolic obesity with normal body weight. So it is not just overconsumption that causes problems, not only the amount of food you eat, but also what type of food you eat. (Why your friend loses weight, but you do not)

Research has shown that a person gains weight faster from a 1000-calorie meal of processed foods than from a 1000- calorie meal of non-processed foods. This has to do with the disruptive effect of processed foods on the mitochondria* in the body. This is why you cannot out-train a bad diet: it is about the functioning of the mitochondria and not just about the calories.[18] (How artificial is your food?)

Unprocessed food has a positive effect on the functioning of the mitochondria and will lead to weight loss. Unprocessed or real food is low in sugar and high in fiber*.

*Mitochondria can be found in almost all cells of the body. They are the energy factories of the cell. Large numbers of mitochondria are found in organs that require a lot of energy, such as the brain, heart, liver and skeletal muscles. One of their functions is to create energy. Our body needs this energy to function properly. The brain needs energy to think, muscles use energy to move. Energy is supplied through nutrients in food. The processing of fuel into energy takes place in the mitochondria. [19]

*Fiber plays an important role in the functioning of the gut and reducing the risk of chronic diseases such as cardiovascular disease, type 2 diabetes, and cancer. Whole grain products, vegetables, fruit, nuts, and legumes contain a lot of fiber. The recommended daily amount for adults is 30 to 40 grams. 1 spoon of oatmeal contains approximately 1 gram of fiber. [20]

Improve your health with a Mediterranean diet

A healthy lifestyle enhances physical and mental health. By eating unprocessed real food, you can decrease your risk of chronic diseasesand of weight gain. Real food means food that is low in sugar, salt, and fat and high in fiber. Food that you prepare yourself and that, for the most, is not wrapped in paper, plastic or tin, and that does not have a long list of ingredients.

Do not be fooled: although fruit is considered a real food, huge amounts of fruit also mean huge amounts of sugar and fructose. Your body considers all types of sugar the same, whether it comes from a cookie or an apple. Real and natural does not always mean healthier. Moderation is key. This means a balanced nutritional pattern that contains all food groups in moderation and that you can maintain your entire life.

Every diet works in relation to weight loss, whether it is ketogenic, intermitted fasting, military, or whatever. Every diet also has the same characteristics: it leaves out certain food groups and therefor also leaves out nutrients, vitamins and minerals. And every diet has the same outcome: in most cases the weight loss is temporary and you will end up with a heavier weight than before the start. Furthermore, also starvation and fasting can eventually lead to non-alcoholic fatty liver.[21] (How important is breakfast?)

Extensive research has shown that a Mediterranean diet, in combination with exercise and three cups of filtered black coffee every day, can have positive health effects in terms of morbidity and mortality.[22]  The Mediterranean diet includes a great variety of foods, which are eaten in moderation and within a positive social environment. It contains a high intake of fruits and vegetables, whole grains, legumes, nuts, fish, white meats and olive oil, a moderate consumption of fermented dairy products and a low intake of red meat. The diet is low in saturated fats and animal protein. It is high in antioxidants, fiber, and monounsaturated fats, and exhibits an adequate omega-6/omega-3 fatty acid balance. The health benefits can be explained by antioxidants, fiber, monounsaturated and omega-3 fatty acids, phytosterols from plants, and probiotics.[23]

With a Mediterranean diet, is it still a matter of finding out what works for you. Research has shown that even identical twins respond differently to the same (real) food. This is due to the characteristics of the individual, among which the microbiome. (Your poop tells it all). Just like a Western diet can impact our genome in a negative way, the Mediterranean Diet can interact with the genome and have a protective effect as well as reduce the risk of disease in the most genetically susceptible individuals.[24]

Practical tip

It does not have to be very complicated: Just stay away from sugar and processed food. From there on you can start to find out what real food works for you by tracking your nutritional habits to get insight in your food choices and behavior, and by recording your physical and mental health. Eat real food that supports your body and mind, avoid processed food and sugar that sickens you.  

Create your own health!©


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[2] Maarten Tushuizen. Leververvetting. Een omvangrijkprobleem. (nov 2021). Jubileum jaarcongres De Week van Arts en Leefstijl:’10 jaar Leefstijl, natuurlijk!’; 11 december 2021.

[3] Idem

[4] Idem

[5] Idem

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[7] Maarten Tushuizen. Leververvetting. Een omvangrijk probleem. (nov 2021). Jubileum jaarcongres De Week van Arts en Leefstijl: ’10 jaar Leefstijl, natuurlijk!’

[8] Geraadpleegd 11 december 2021.; C.T.M. van Rossum et al. RIVM. The diet of the Dutch. Results of the Dutch National Food Consumption Survey 2012-2016. Report 2020-0083.

[9] Geraadpleegd 11 december 2021.

[10] Geraadpleegd 11 december 2021.

[11] Geraadpleegd 11 december 2021;,%2C%20siropen%2C%20vruchtensappen%20en%20vruchtenconcentraat. Geraadpleegd11 december 2021

[12] Geraadpleegd 11 december 2021

[13] 11 december 2021;,vormt%20fructose%20de%20disacharide%20sacharose. Geraadpleegd 11 december 2021.

[14] DiNicolantonio JJ, Mehta V, Onkaramurthy N, O'Keefe JH. Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity. Prog Cardiovasc Dis. 2018 May-Jun;61(1):3-9. doi:10.1016/j.pcad.2017.12.001. Epub 2017 Dec 8. PMID: 29225114; Collison KS, ZaidiMZ, Saleh SM, Inglis A, Mondreal R, Makhoul NJ, Bakheet R, Burrows J, MilgramNW, Al-Mohanna FA. Effect of trans-fat, fructose and mono sodium glutamate feeding on feline weight gain, adiposity, insulin sensitivity, adipokine andlipid profile. Br J Nutr. 2011 Jul;106(2):218-26. doi:10.1017/S000711451000588X. PMID: 21429276.

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[19] Geraadpleegd 11 december 2021

[20] Geraadpleegd 11 december 2021

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[23] Urquiaga I, Echeverría G, Dussaillant C, Rigotti A. Origen, componentesy posibles mecanismos de acción de la dieta mediterránea [Origin, components and mechanisms of action of the Mediterranean diet]. Rev Med Chil. 2017Jan;145(1):85-95. Spanish. doi: 10.4067/S0034-98872017000100012. PMID: 28393974.

[24] Corella D, Barragán R,Ordovás JM, Coltell Ó. Nutrigenética, nutrigenómica y dieta mediterránea:una nueva visión para la gastronomía [Nutrigenetics, nutrigenomics and Mediterranean diet: a new vision for gastronomy]. Nutr Hosp. 2018Jun 12;35(Spec No4):19-27. Spanish. doi: 10.20960/nh.2120. PMID: 30070117. Tim Spector. Personalised Nutrition. (nov 2021). Jubileum jaarcongres De Week van Artsen Leefstijl: ’10 jaar Leefstijl, natuurlijk!’