Want to Lose Weight-It’s Not Complicated-Part II-Forget Fructose
If you want to lose weight then you need to control sugar consumption, plain and simple. One sugar in particular, fructose, clearly requires attention. This sugar has raised controversy. The proponents of fructose and high fructose corn syrup (HFCS) namely the packaged food industry, corn manufacturers and dubious medical experts, will tell you that fructose and HFCS are safe. They will make the comparison between glucose and fructose, saying that they are both classified as a simple sugar. They both share the same molecular make-up… that being C6-H12-O6. Furthermore, they will tell you that fructose is the sugar found in fruit, and we know that everybody agrees that fruit should be part of a healthy diet, therefore establishing that fructose is not only safe but it’s actually good for you.
However, once we get past these minor similarities and review some biochemistry we’ll discover some major differences. This includes the following:
When the body increases its blood sugar level, it uses cortisol, adrenaline or glucagon, to put glucose not fructose into the blood.
When the body needs to lower blood sugar level, it takes insulin which grabs glucose not fructose for storage.
When the body wants to metabolize food for energy, via the Kreb’s Acid Cycle it uses glucose not fructose, as its only carbohydrate source.
The only carbohydrate the brain uses is glucose not fructose; in fact, fructose never crosses the blood brain barrier (BBB).
Every cell in the body has a receptor specifically made for glucose not fructose; in fact there are no receptor sites for fructose.
The body recognizes glucose not fructose as the universal carbohydrate fuel that the body uses.
The only way that fructose gets metabolized is through the liver. So what do you call it when you consume something that can only get processed by the liver? It’s called a toxin. Dr. Robert Lustig, a pediatrician endocrinologist, who’s video entitled Sugar-The Bitter Truth (and certainly worth watching) calls it a poison.
Besides their functional differences, there are also structural differences (shown below) between these two sugars. Glucose contains a six-ringed structure while fructose is a five-ringed structure.
In biochemistry structure is key to function, for example the difference between a healthy double bond known as a cis-bond and a deleterious trans-fat is structure.
Another clever tactic that food manufacturers and advertisers use is telling us that table sugar and HFCS are metabolized “nearly the same”. However, there is some truth to this in that both are bad. To review. Table sugar also known as sucrose (shown below), is a disaccharide, meaning that it is composed of two sugars. The two sugars, glucose (left) and fructose (right), is divided equally, while HFCS is 55% fructose; all else is the same. When you consume sucrose, the enzyme sucrase then cleaves it into their respective sugars. At this point these two sugars go their own separate pathways.
The Problem with Fructose
Fructose is cheap and therefore is used extensively in packaged and fast food products. Secondly, it’s sweeter than glucose thus making it more addictive. These components of being so cheap and highly sweet makes it a dream come true, that is for food manufacturers, not you.
Fructose is also used in food products that we don’t associate with sweets. Foods like crackers, soups, ketchup, mustard, gravies, sauces, bread, hot dog/hamburger buns are also made with this sugar. Fructose is used so extensively that in Dr. Lustig’s excellent lecture, “Sugar-The Bitter Truth” points out that there are only seven fructose-free products in the entire McDonald’s menu. Among those foods, fructose-free, include water, coffee (without any sugar taken), french fries and hash browns (for the others you need to watch the video). (1) And we all know how healthy those fries and hash browns are since they are bathed and cooked with cheap pro-inflammatory cooking oil.
Fructose causes an elevation in triglycerides (TG) also known as very low-density lipoprotein (VLDL), which is a component of the cholesterol panel. An increased consumption of fructose has shown to be parallel to the increased incidence of obesity and diabetes mellitus (2). Having a TG level that is more than half of the total cholesterol is considered Metabolic Syndrome which places you as pre-diabetic.
Fructose has a major role in promoting obesity because it impairs the hormone, leptin. Leptin, is known as the satiety hormone. It is made in adipose (fat) tissue (thus making adipose tissue an endocrine organ) and works in the hypothalamus to shut down food consumption. When leptin is working properly it tells the brain that you had enough food, you’re satisfied, satiety is reached, and it shuts down appetite therefore limiting unnecessary calories. Unfortunately when this hormone is impaired, known as leptin resistance (not leptin deficiency), the signaling of satiety is not reached, and overeating and ultimately obesity occur. Leptin resistance occurs when there is high fructose consumption or an elevated TG level; both are influenced by fructose.
Have you ever wondered why sedentary people can devour those super-sized meals (e.g. double and triple whoppers, 50 oz. Big Gulps) without any difficulty? It’s because they are leptin resistant. The irony is that even shortly after a meal, the leptin resistant person still feels hungry. This is central to the obesity problem and fructose is an accomplice. When you consider the extensive usage of fructose in fast foods, a typical (not extravagant) meal of a Big Mac (no cheese), medium fries and a 16 oz vanilla shake contains 1,470 calories; 3,500 calories equals a pound of fat (3). That is more than a pound of fat in just three meals!
As long as supermarkets, fast food restaurants, and convenience stores continue offering products with fructose, expect, as the evidence shows, obesity to increase. While the food manufacturers make the argument that glucose and fructose are “nearly the same”, the “nearly the same” argument has no basis when you focus on biochemistry, physiology or endocrinology whereby the body purposely and deliberately always chooses glucose as its carbohydrate fuel thus leaving fructose for the liver to treat it as it is …a toxin. So if your goal is to lose weight then one thing must be implemented: forget fructose.
References:
1) Sugar-The Bitter Truth, lecture at the University of California, San Francisco Robert H. Lustig, M.D., May 26, 2009
2) Fructose impairs glucose-induced hepatic triglyceride synthesis, Huang, D., et. al. Lipids Health Dis. 2011 10:20.
3) McDonald’s USA Nutrition Facts for Popular Menu Items
Next time: Part III: Artificial Sweeteners
Joel Berger, MS, DC, DABCN August 2013 ©