The “F” Word of Fitness

The nutrition and fitness world seem to periodically target a single nutrient as the root of all health problems. In the 80s the enemy was dietary fats and in the 90s there was a transition towards carbohydrates. Soon after trans-fatty acids became the one thing people must not eat. Today, high fructose corn syrup (HFCS) is the doer of all evil in the nutrition world; responsible for obesity, diabetes and a host of other health problems. Now, while the research does indicates that high levels of HFCS in the diet can lead to certain health problems, the threat has no doubt been stretched out of context. Nowhere is this more evident than in the fitness industry where everything containing fructose is being isolated and removed from the diet, including fruit! Are the rumors true? Is fruit making you fat? Not likely.  Apart from ingesting excessively high levels of fructose, the fructose scare seems to be inflated slightly.

Let’s start by quickly outlining what fructose is – the “F” word of Fitness. Fructose is a monosaccharide, or, simple sugar since it is made up of only one sugar molecule. As most people are aware, fructose makes up a portion of the carbohydrates in fruit. Like many other dietary carbohydrates, fructose is converted to glucose within the body. With fructose, this process is done by the liver. Fructose is almost never found in the bloodstream in large quantities; it is either stored in the liver as glycogen before being converted to glucose and released into the bloodstream, or simply converted to glucose and released after consumption. Unlike glucose, fructose is digested slowly by the body and doesn’t have significant effects on blood sugar levels or insulin response. Initially, this effect jump started thoughts that fructose was a superior sweetener to other simple sugars, especially for diabetics; however, it turns out that this reasoning isn’t entirely true, as excess fructose can cause negative health problems (Please note the word excess: it would require an insanely large amount of fruit to be consumed at once to cause problems in the body).

The problems begin to occur when high amounts of fructose (generally above 50 grams) are consumed at once. It is at this level when the liver begins to convert fructose to triglycerides (fat) and other negative health issues occur (including lack of production of leptin, an important hormone associated with the long term energy balance). In other words, excessive amounts of fructose can lead to the creation of fats in the liver and the breakdown of our energy balance and fat regulating system. As a result, the consumption of high fructose sweeteners can lead to a number of health problems including central obesity, increased in bad cholesterol, decreased in good cholesterol, high triglycerides, and poor appetite control.

Now let’s take a step back for a moment. When we talk about high levels of fructose (above 50 grams), it doesn’t necessarily mean we should be removing fruit from the diet. Fruit has received some bad press within the fitness world since it contains fructose; however, one would have to eat an unreasonable amount of fruit to reach troublesome amounts of fructose (try 5 to 6 medium apples in one sitting). In reality, if one wants to limit the amount of fructose in their diet they should start by eliminating sugary sodas, fruit drinks, and other high sugar items. A single serving of fruit juice with HFCS can contain around 50 grams of fructose. The majority of fructose in our diet comes from HFCS as an additive in foods and sucrose (table sugar) which is made of glucose and fructose. Before you consider eliminating fruit from the diet consider all the health benefits it provides.

Fruit can help combat hunger, which is especially good for people who are dieting and are on calorie restricted diets. As well, fruit is high in fiber and nutrients. It’s important to not make the mistake that the small amount of fructose found in fruit will be problematic. It’s highly unlikely that consuming whole, unprocessed, fresh fruits will promote energy imbalances and body fat gains. However, it is likely that over consumption of fructose-rich fruit juices and other foods will cause these problems.

Now, although the anti-fructose craze is over-hyped somewhat within the fitness community, clearly health problems can occur when fructose in regularly over-consumed. In this sense, consider limiting intake of HFCS and continue moderately eating healthy, fiber-rich fruit.



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