The harmful effects of sugar go way beyond empty calories.
Added sugar is so unhealthy that it is probably the single worst ingredient in the modern diet.
Here are the top 9 reasons to avoid sugar.
The reason added sugar (and its evil twin... High Fructose Corn Syrup) is bad for you, is that it supplies a very large amount of fructose.
Sugar (and HFCS) are half glucose, half fructose. Glucose is essential and can be metabolized by pretty much every cell in the body. If we don't get it from the diet, our bodies make it from proteins and fat.
Fructose, however, is not essential to our functioning in any way.
The only organ that can metabolize fructose is the liver, because only the liver has a transporter for it (1).
When large amounts of fructose enter the liver and it is already full of glycogen, most of the fructose gets turned into fat (2).
This process is probably one of the leading causes of the epidemics of many chronic, Western diseases.
I'd like to point out that this does NOT apply to fruit, which are a real food with vitamins, minerals, fiber, lots of water and are very difficult to overeat on.
Bottom Line: The only organ that can metabolize fructose is the liver. When we eat a lot of fructose, many things in the body start to go wrong.
Sugar IS empty calories. No doubt about that.
Most high-sugar foods like pastries, sodas and candy bars contain very little essential nutrients.
People who eat them instead of other more nutritious foods will probably become deficient in many important nutrients.
Bottom Line: Most products with added sugars in them contain very little nutrients and can therefore be classified as "empty" calories.
When we eat fructose, it goes to the liver.
If liver glycogen is low, such as after a run, the fructose will be used to replenish it (3).
However, most people aren't consuming fructose after a long workout and their livers are already full of glycogen.
When this happens, the liver turns the fructose into fat (2).
Bottom Line: Eating a lot of added sugar (fructose) can cause deposition of fat in the liver and lead to Non-Alcoholic Fatty Liver Disease.
Most of the fat generated in the liver gets shipped out as Very Low Density Lipoprotein (VLDL) particles.
These particles are rich in triglycerides and cholesterol.
In a controlled study, people were assigned to drink 25% of calories as either a glucose-sweetened drink or a fructose-sweetened drink for 10 weeks (7).
The fructose group had:
- Increases in blood triglycerides
- Increases in small, dense LDL and oxidized LDL (very, very bad)
- Higher fasting glucose and insulin
- Decreased insulin sensitivity
- Increased fat in the abdominal cavity (visceral fat)
Basically, 25% of calories as fructose significantly harmed blood lipids and caused features characteristic of the metabolic syndrome, which is a stepping stone towards obesity, heart disease, diabetes and a (short) lifetime of poor health.
Bottom Line: Consuming a large part of calories as fructose can lead to serious adverse effects on blood markers in as little as 10 weeks.
The main function of insulin is to drive glucose from the bloodstream into cells.
But when we eat a Western diet, the cells tend to become resistant to the effects of insulin.
When this happens, the pancreas start secreting even more insulin to remove the glucose from the bloodstream, because elevated blood glucose is toxic.
This is how insulin resistance leads to elevated insulin levels in the blood.
But insulin also has another important function... it tells the fat cells to pick up fat from the bloodstream and to hold on to the fat that they already carry.
This is how insulin causes obesity.
When the body becomes even more resistant to insulin, the beta cells in the pancreas eventually become damaged and lose the ability to produce sufficient insulin. This is how you get type II diabetes, which now afflicts about 300 million people worldwide.
Bottom Line: Excess fructose consumption can lead to insulin resistance, a stepping stone towards obesity and diabetes.
Excess sugar consumption has been associated with many Western diseases.
If anything, sugar is the single largest contributing factor to the poor health of affluent nations.
Every time sugar (and refined flour and vegetable oils) enter a population's diet, these people become sick.
Sugar has been associated with:
- Obesity. Sugar causes weight gain via various mechanisms, including elevated insulin and leptin resistance (11, 12).
- Diabetes. Sugar is probably a leading cause of diabetes (13, 14, 15).
- Heart disease. Sugar raises the bad cholesterol, triglycerides and causes various other issues that can ultimately lead to heart disease (16, 17).
Bottom Line: Excess sugar consumption has been associated with many serious diseases, including obesity, type II diabetes and cardiovascular disease.
An area in the brain called the Hypothalamus is supposed to regulate our food intake.
In a study published in 2013, two groups drank either a glucose-sweetened drink or a fructose-sweetened drink (18).
The glucose drinkers had decreased blood flow in the hypothalamus and felt satiated, while the fructose drinkers had increased blood flow in this area of the brain.
The fructose drinkers felt less satisfied and were still hungry.
Another study revealed that fructose didn't reduce levels of the hunger hormone ghrelin like glucose. The more ghrelin, the hungrier you are (19).
Bottom Line: Studies comparing fructose and glucose show that fructose does not induce satiety like glucose, which will contribute to a higher calorie intake.
When we eat sugar, dopamine is released in the brain, giving us a feeling of pleasure.
This is actually how drugs of abuse like cocaine function (20).
Our brain is hardwired to seek out activities that release dopamine. Activities that release an enormous amount of it are especially desirable.
In certain individuals with a certain predisposition to addiction, this causes reward-seeking behavior typical of addiction to abusive drugs.
Studies in rats demonstrate that they can in fact become physically addicted to sugar (21).
This is harder to prove in humans, but many people consume sugar and other junk foods in a pattern that is typical for addictive, abusive compounds.
Bottom Line: Sugar, due to its powerful effects on the reward system in the brain, can lead to classic signs of addiction.
Leptin is a hormone that is secreted by our fat cells. The more fat we have, the more leptin is secreted.
This is supposed to function as a signal to tell the brain that we're full and need to stop eating. It is also supposed to raise our energy expenditure.
Obese individuals actually have high levels of leptin, but the problem is that the leptin isn't working.
This is called leptin resistance and is a major reason why people eat more calories than they burn and become obese.
Fructose is a known cause of leptin resistance, both because insulin blocks leptin signalling in the brain and because fructose raises blood triglycerides which also blocks the effects of leptin (22, 23, 24).
This makes our brain think that the fat cells are empty and that it needs to keep eating.
Willpower is very weak compared to the leptin-driven starvation signal.
This is the reason people can't just "eat less, move more" and live happily ever after.
To reverse leptin resistance and make the brain WANT to eat less, sugar has to go.