Sugar is the generalized name for sweet, short-chain, soluble carbohydrates, many of which are used in food. They are carbohydrates, composed of carbon, hydrogen, and oxygen.
There are various types of sugar derived from different sources. Simple sugars are called monosaccharides and include glucose (also known as dextrose), fructose and galactose. The table or granulated sugar most customarily used as food is sucrose, a disaccharide. (In the body, sucrose hydrolyses into fructose and glucose.) Other disaccharides include maltose and lactose.
There are various types of sugar derived from different sources. Simple sugars are called monosaccharides and include glucose (also known as dextrose), fructose and galactose. The table or granulated sugar most customarily used as food is sucrose, a disaccharide. (In the body, sucrose hydrolyses into fructose and glucose.) Other disaccharides include maltose and lactose.
Sugar has recently been strongly linked to diabetes, obesity and weight gain, and there is no doubt that a high intake of sugar and sugar containing foods can contribute to weight gain. However, does sugar deserve the ‘poison’ reputation that it has acquired in recent times?
Why sugar can cause us to put on weight
Sugar contains calories, thus, as with any food, if we eat too much of it we will gain weight. To maintain weight we need to burn off the same amount of calories as we are consuming from food, so if we eat more than we burn, weight gain will follow.
Sugar (sucrose) and high fructose corn syrup contain two molecules: glucose and fructose.
Glucose is absolutely vital to life and is an integral part of our metabolism. Our bodies produce it and we have a constant reservoir of it in the bloodstream.Every cell in the body can use glucose for energy. If we don’t get glucose from the diet, our bodies produce what we need out of proteins and fats.
Fructose, however, is very different. This molecule is not a natural part of metabolism and humans do not produce it.In fact, very few cells in the body can make use of it except liver cells.
When we eat a lot of sugar, most of the fructose gets metabolized by the liver. There it gets turned into fat, which is then secreted into the blood.
1. Fructose Causes Insulin Resistance
It is one of the key hormones that regulate human metabolism and energy use.Insulin is secreted by the pancreas, then travels in the blood to peripheral cells like muscle cells.Insulin sends a signal to these cells that they should put transporters for glucose onto their surface, thereby allowing glucose to get into the cells where it can be used.
When we eat a high carb meal, glucose levels go up. Excess glucose is toxic so insulin rapidly goes up in order to get the glucose out of the bloodstream and into the cells.If we didn’t have insulin or it wasn’t functioning correctly, blood glucose would reach toxic levels.In healthy people, this mechanism works very well and enables us to eat meals that are high in carbohydrates without our blood glucose going out of whack.
2. Fructose Causes Resistance to a Hormone Called Leptin
Fructose also causes weight gain by its effects on a hormone called leptin.Leptin is secreted by fat cells. The bigger the fat cells, the more leptin they secrete. This is the signal your brain uses to determine how much fat it has stored for a rainy day.When we eat food, some of it gets stored in the fat cells. This makes the fat cells get bigger and secrete more leptin.When the brain senses the increased leptin, it “sees” that we have enough fat stored and that we don’t need to eat.
This is the elegant mechanism designed by nature to make us stop being hungry and eat less when there is plenty of fat in the our fat cells, which is supposed to prevent us from becoming obese.
More fat = more leptin = we have enough energy = don’t need to eat. Simple.
In order to be able to eat less, we have to get rid of the leptin resistance, so that our brain “sees” all the fat that we have stored.
3. Fructose Does Not Induce Satiety in The Same Way as Glucose
The way the body and brain regulate food intake is extremely complex and involves multiple hormones and neural circuits.There is a region in the brain called the hypothalamus, where all of these signals are interpreted.This is where leptin (discussed above) functions in the brain, along with various neurons and other hormones.They gave 20 healthy volunteers either a glucose-sweetened drink or a fructose-sweetend drink, scanned their brains and asked them a bunch of questions.It turned out that the glucose drink lowered blood flow and activity in the hypothalamus (where food intake is controlled) while the fructose drink did not.
The glucose drinkers felt less hungry and more satiated compared to the fructose drinkers, who didn’t feel satisfied at all and were still somewhat hungry.This implies that the fructose-sweetened drink, despite having the same calories as the glucose drink, did NOT increase satiety as much.
4. Sugar Makes You Addicted
Sugar causes opiate and dopamine activity in the reward centers of the brain, just like other drugs of abuse like cocaine.These studies were done in rats, which are good representatives of humans because they become addicted to abusive drugs in the same way as we do.
A quote from the study:
“The reviewed evidence supports the theory that, in some circumstances, intermittent access to sugar can lead to behavior and neurochemical changes that resemble the effects of a substance of abuse.”
The evidence is very strong for sugar being downright addictive. It makes perfect sense given that it affects the same neural pathways as drugs of abuse.
Eating sugar gives us “pleasure” and releases opiates and dopamine in the reward system of the brain, specifically in an area called the Nucleus Accumbens. These are the same areas stimulated by drugs of abuse like nicotine and cocaine.
Why sugar is not the only thing that will make us put on weight
Although sugar is definitely a source of calories and can have a negative effect on our health and weight when consumed in excess, there are plenty of other things that have been associated with the growing levels of obesity in our society.
A lack of physical activity means that we burn less calories than we did in the past, whilst high intakes of processed foods that are not only high in sugar but also in fat, particularly trans and saturated types has probably contributed to some degree in many populations as well.
Although a diet containing moderate levels of healthy fat is now considered healthy, it is still the nutrient with the highest amount of calories per gram and therefore can be a major consideration in weight gain if consumed in large amounts.
Why not all sugar is bad?
Whilst sugar is unlikely to ever be considered a healthy nutrient, given the lack of nutritional value in its pure form, sugar is often found in many foods that do contribute to better health. Fruit, for example contains sugar in the form of fructose and glucose, however it also contains fiber and a wide array of nutrients, making it a valuable part of a healthy diet.
Similarly milk, which contains sugar in the form of lactose, also provides calcium and valuable protein that contributes to satiety. It has been suggested that whilst milk, fruit and juice and soft drinks all contain sugar, the latter two are more likely to contribute to obesity due to their lack of protein which helps to fill you up and stop you from overeating.
Should you quit sugar?
A little bit of sugar in your diet is unlikely to be a huge problem, and certainly if it is in the form of a food that provides important nutritional value. Reducing your sugar intake by eliminating added sugars and processed foods and drinks that are very sweet may be a good way to lose weight, control cravings and reduce risk of lifestyle diseases, however diets that eliminate any sugar containing food such as fruit is probably too extreme and is likely to put you at risk of deficiencies in other nutrients.
References used in this article
