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The Unsweet Truth About Sugar & Weight Gain

Sweet to taste but not-so-sweet for health, find out the truth about sugar and how it can lead to weight gain.

The Unsweet Truth About Sugar & Weight Gain


Just a spoonful of sugar makes the medicine go down, right? Mary Poppins might have been onto something... 

Only, in this context, that jingle means something entirely different. In this case, one (or many) spoonfuls of sugar a day cause medications to "go down." High sugar consumption is associated with nearly every single chronic disease, autoimmune conditions, and even acute sickness. 

So, perhaps sugar is not so sweet after all...

Learn the unsweet truth about the connection between sugar and weight gain, chronic disease risk, and other health concerns.

Understanding Glucose and Insulin

By now, many people know that sugar does not support health, but they do not necessarily know why. Many understand that sugar is a major driving cause of obesity, but do not know how this happens. 

For this reason, it is imperative to understand the relationship between glucose and insulin. Both of these are undeniably responsible for many health concerns.

What Is Glucose?

Glucose is one of the simplest forms of carbohydrate. All carbohydrates must be broken down into glucose before cells can use it to make the only form of usable energy known as ATP. However, not all glucose is created equal.

Essentially, the body breaks down natural carbohydrates derived from fruits, vegetables, and other plant foods differently than refined carbohydrates found in processed and packaged food. This is largely because those plant foods also contain substances like antioxidants and fiber that slow the release of glucose and therefore the secretion of insulin as well. Conversely, refined sugar is rapidly released into the bloodstream, causing a sharp spike in insulin. More on insulin shortly!

Back to glucose - Carbohydrates are necessary for survival. Two major types of cells, red blood cells and the brain, can only use glucose as fuel. All other cells can use fat for energy, though they all prefer glucose. 

As an aside, people are able to "survive" on very low carbohydrate diets like keto. This is because the body essentially learns how to efficiently turn fat into glucose via ketones, which red blood cells and the brain can then use.

In summary, glucose is not inherently bad. Repeat again: Carbs are not the worst! However, the quality of carbohydrates certainly matters because of their different insulin responses.

What Is Insulin?

Insulin is a hormone made by the beta cells of the pancreas. It exerts several functions, but the most important one is to transport glucose into cells.

When a carbohydrate is consumed, the digestive tract will break it down into glucose before it enters the bloodstream. When the brain detects glucose, it sends signals to the pancreas to secrete insulin. Insulin is then supposed to transport the glucose into cells from the blood. Glucose cannot feed cells without insulin.

Insulin also helps balance blood glucose/sugar by signaling the liver to uptake extra glucose circulating in the blood. Note that this only occurs when more carbohydrate is consumed than cells need. 

If blood sugar drops too low, related to exercise/physical activity, fasting, or other causes, the liver secretes the stored glucose into the bloodstream. This is where insulin repeats the process outlined just above.

Does Sugar Cause Weight Gain?

The short answer is yes. But once again, the combination of eating too much sugar (and empty calories overall) and insulin can cause weight gain.

First understand that insulin is an anabolic hormone, which anabolic essentially refers to building and storing. In addition to promoting glucose uptake, it also encourages glycogenesis (the building of glucose molecules into glycogen to be stored) and lipogenesis (the building of fat molecules to be stored).

In other words, insulin spurs metabolic mechanisms that build and then store glucose in muscles and the liver and fat in adipose (fat) tissue.

But, the overconsumption of sugar is what causes too much insulin release that ultimately encourages the storage of fat, aka weight gain. This also makes it more difficult to achieve weight loss.

If someone's cells need carbohydrates, which is the case after long fasts (sleeping) and intense exercise, then after eating carbohydrates, insulin will help transport them into cells to feed them. If there is remaining glucose circulating in the blood, it will replenish muscle stores if needed and the rest will go to the liver to be stored for later. This is a normal, healthy metabolic function.

However, if someone largely over-consumed carbohydrates, the above process still occurs but additional glucose swims around the blood. Extra circulating glucose glycosolates cells, ultimately reducing their function. The body will also convert that extra glucose into fat molecules to be stored, which greatly playing a role in obesity risk. 

Does Sugar Cause Diabetes?

This mechanism of action is very closely related to glycosylation. But before that, understanding the two different types of diabetes is vital. Although their mechanisms of action are similar, the root causes are different.

Type 1 Diabetes

Type 1 diabetes is caused by an autoimmune reaction that causes the pancreas to stop creating insulin. Type 1 is typically diagnosed in childhood between the ages of 5-18 and requires exogenous insulin in some form. 

The onset of type 1 diabetes is not directly associated with high sugar consumption and is more correlated with genetics.

Type 2 Diabetes

Type 2 diabetes is a metabolic condition caused by a variety of risk factors. However, poor eating habits and overconsuming poor quality and added sugar are the strongest. Typically diagnosed later in life, type 2 diabetes is being diagnosed in more children than ever these days, and may or may not require exogenous insulin.

The mechanism described in the weight gain section still applies here, but there is another important aspect to understand. In addition to causing weight gain, overconsuming sugar can eventually make cells resistant to insulin - hence the well-known phrase insulin resistance.

Remember how glycosylation decreases the function of cells? Well, too much sugar too often makes cells less sensitive to insulin - or reduces insulin sensitivity. 

This means that even as more insulin is secreted, the cells will not uptake the glucose, leaving it to circulate in the blood and wreak the havoc already described. This also tires the pancreas, leading to less insulin production. In this case, a type 2 diabetic would require exogenous insulin.

All in all, the environment of frequently overconsuming sugar causes increased insulin secretion. Cells become resistant to the hormone, which then leads to remaining glucose in the blood, and that promotes weight gain. 

The cycle is viscous but it can be broken through diet and lifestyle changes. This also means that type 2 diabetes is essentially reversible as long as the pancreas still has a remaining function. 

The Last Note on Sugar & Weight Gain

The overconsumption of glucose and the resulting insulin secretion is most often associated with developing type 2 diabetes and weight gain. However, it cannot be repeated enough that it is also correlated with an increased risk of many, many other diseases and conditions like:

• High blood pressure
• Elevated "bad" cholesterol levels
• Heart disease and stroke
• Cancer
• Cystic acne
• Depression
• Fatty liver
• Accelerated aging

And, all of these conditions are also associated with obesity.

Thus, as sweet as sugar tastes, over-consuming the refined, processed versions inextricably leads to poor health outcomes. Although a spoonful might help cough medicine go down, too many spoonfuls can definitely disrupt good health. 

References:

Buppajarntham S. Insulin: Reference Range. Medscape. Published April 2, 2021. https://emedicine.medscape.com/article/2089224-overview#a1.

Higuera V. About Insulin: What It Is, How It Works, and More. Healthline. Updated May 7, 2019. https://www.healthline.com/health/type-2-diabetes/insulin.

Kubala J. 11 Reasons Why Too Much Sugar Is Bad for You. Healthline. Written June 3, 2018. https://www.healthline.com/nutrition/too-much-sugar#TOC_TITLE_HDR_2.

Reily C. Glycosylation in Health and Disease. Nature News. Published March 11, 2019. https://www.nature.com/articles/s41581-019-0129-4?proof=t.

Sydney Lappe's Photo
Written By Sydney Lappe, MS, RDN. Published on November 07, 2012. Updated on June 20, 2022.

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