Replies

Is sugar making us fat?

Neither sugar (sucrose, which is glucose and fructose in a 1:1 ratio) nor high fructose corn syrup (which has a greater than 1:1 ratio of fructose) is making us fat. A diet with an energy intake that exceeds an individual's energy output is what makes him fat.

The truth is relatively simple, but that won't stop this thread from being filled with outlandish nonsense. The following can be used to separate fact from nutzoid nutracrap.

Fructose* (a six carbon sugar) enters the glycolytic pathway and is used in exactly the same way as glucose (another isomer of the same molecular formula and known as dextrose, grape sugar, or corn sugar). In fact, glucose is phosphorylated on the 6 carbon to become fructose 6-phosphate. Fructose 6-phosphate is phosphorylated again on the 1 carbon to become fructose 1,6 diphosphate. Dietary fructose (whether it comes from sucrose or from honey or from fruit or from high fructose corn syrup) is phosphorylated on the 1 carbon and then on the 6 carbon, ending up as fructose 1,6-diphosphate, the same as glucose.

Neither glucose nor fructose is made into fat in the human body. Fat cannot be converted into glucose. The human body makes very, very little fat de novo. The way one gains fat is principally from fat in the diet that is stored in adipose tissue. If you took a sample of all the fats you ate over a year's period and compared their types and relative quantities to the fat in a tissue sample of your adipose tissue, you'd find they were almost exactly the same.

The way you accumulate such fat has to do with your body's storage capacity for the three macro-nutrients (proteins, carbohydrates, and fat) when faced with dietary excess. The body has no real storage form of protein. Protein intake in excess of physiological needs for protein synthesis results in the constituent amino acids being deaminated and catabolized either in the glycolytic or lipolytic pathways depending on the type of amino acid. Carbohydrate intake can be buffered through about three days worth of storage in the form of glycogen, a polymer of glucose molecules. Relative to proteins and carbohydrates, fat has almost unlimited storage capacity.

When ones energy intake exceeds output, the body compensates by prioritizing the catabolism of macronutrients. Proteins have most immediate priority, followed by glucose, followed by fats. If the continued excess of caloric intake threatens to overtax the glycogen storage capacity, the body shifts substrate usage away from fat oxidation (nearly all your resting metabolic rate is accounted for by fat oxidation) and toward glucose oxidation. The result is that energy intake that exceeds energy output is preferentially saved by the storage of dietary fat.

*So any time you have one unit of sucrose, 1/2 of that is fructose. And it is principally the fructose in sugar, not the glucose, that makes it taste sweet. This is why it takes much less fructose to sweeten something to the same degree as it does sucrose. Maltose is two molecules of glucose. Lactose is one molecule of glucose and one of galactose. All hexose dietary sugars (fructose, glucose, and galactose) are eventually converted into fructose 1,6-diphosphate.

The truth is relatively simple, but that won't stop this thread from being filled with outlandish nonsense.

Like the two recent studies in the New England Journal of Medicine that support Atkins' diet? Sheesh.

The truth is relatively simple, but that won't stop this thread from being filled with outlandish nonsense

That's what I say! I believe for 99% of people it's as simple as you eat too many calories and you don't exercise enough to burn them off!

I don't care what kind of calories they are; fat, sugar, carbos... they're all calories. Although, I do believe in eating a healthy diet with mostly low fat foods and plenty of fruits and vegetables for your own health. You can still clog your arteries whether you're thin or not.

I believe the number one thing to staying healthy and unfat is regular exercise (aerobic activity and weight training)! A decent diet and proper rest don't hurt either.

I eat everything... mostly a balanced diet with tons of carbos, but also sugar, chips, cookies, BEER, etc. I'm in great shape because I've run 40 miles per week and done weight training for the past 30 years. I'm 45, can still run a mile under 4:50 at the present time (Trying to get back to sub 4:40) and can bench press 300 lbs. I weigh 170ish at around 6'. My brothers on the other hand are overweight and in BAD shape physically (IMO)! One is 6' 215-220 and the other is 5' 11" 250-260! They eat less than me, but do 0-1% exercise a day! Same genes and everything!

Lifestyle is 95% of everyone's problems and that's the TRUTH!! You heard it first or second!

Thanks for the very detailed information on sucrose/fructose. Do you work in the medical field? I only ask because you sound like you might be a doctor.

I've gone about my weight loss plan in a brutish, heavy-handed way. I walk 7-10 miles a day, every day. I do two walks daily of 3-5 miles, one at 5AM and one around noon. I figure that keeps my metabolism going throughout the day. I also keep my calorie intake to about 2000 a day. At my current weight, I reckon I burn 3072 calories a day with normal activity and burn 170 calories a mile walking. Once I reach my target weight of 185, I'll only be burning 2220 each day (based on the formula that a male burns 12 calories per pound per day in normal day-to-day activity). So the free ride is coming to an end. As I get closer to my goal, I'm going to really have to work hard to get those last pounds off.

Once I get to about 225, I'll probably start a weight lifting program to complement my walking. I just don't want to start too soon (with weightlifting) and get an injury that will impede my progress.

... outlandish nonsense ...

AKA The Big Lie, is the sine qua non of group cohesion. It really helps to promulgate the lie if the outlandish nonsense is what the group wants to hear. For example, eating cheese, butter, and meat is better for you than eating beans, vegetables, and whole grains. Of course, this may be true, (especially if you're involved in the sale of dairy products or a meats), but I haven't seen any convincing scientific proof (i.e. long term populations studies) to support the high fat meat based diet over a lower fat plant based diet.