honold said:
here's my question: are calories just calories? i've heard that eating a potato vs eating a potato's worth of pure sugar will actually make your insulin work harder because of the carbs, and i've heard about how complex carbs are worse than regular ones.
honold,
Without getting into excessive detail (partly because I have forgotten the finer points), calories are not just calories. This is especially the case with carbs and sugars, as you have pointed out. The most common measurement for a carb's "evilness" is its Glycemic Index (GI), which is measured in Dextrose Equivalents (DE). Glucose (dextrose) is 100; the higher the number, the faster the carb in question will be broken down and absorbed into the bloodstream, raising glucose levels. Generally, sugars have higher GI values than complex carbs like starches, as it simple sugars don't have to be broken down as much as starches before they are transported across the intestinal lumen and into the bloodstream. I'm sure you can find a table somewhere on the Net. Google Glycemic Index for more details.
Howell,
your first question is related to honold's. Again, this is related to the GI. Sugars have a higher GI and therefore trigger greater insulin release. And of course, insulin is bad. Evil stuff, that anabolic hormone. It not only builds muscle, but it is especially good at building fat as well! Bad insulin. Bad doggy. The key is to minimize insulin release as much as possible. I don't know if Dr. Atkins really knew how insulin worked back in the days when he came up with his Zone Diet, but he had the right idea nevertheless (limit carbs, replace with fat = less insulin release).
The important question that should be on your minds is "what factors affect insulin release"?
Glycemic Index: The higher it is, the faster the offending carb will raise blood glucose levels (which is one part of the insulin release equation).
Glycemic Load: GL = GI x grams of carbs. This is actually a more important metric than GI because it takes the
amount of carbs you eat into account, not just its potency per 50 grams. So, a bowl of spaghetti will obviously have a much higher GL than a tablespoon of glucose, even though glucose has a higher GI than pasta.
Transit Time: This is how quickly food moves through your digestive system and eventually into your bloodstream. The faster things move through your digestive tract, the faster it will spike blood glucose levels and trigger insulin release.
Another important question that you should ask is "what influences transit time?"
The two F's --
Fats and fiber -- increase slow digestion and increase transit time, thereby blunting the insulin response. This is why a big bowl of salad with celery, carrots, cucumbers, tomatoes, etc. lightly tossed with balsalmic vinaigrette is an excellent appetizer!
Osmolarity: Just like Coug pointed out, the optimal (maximal) absorption rate for sugars is achieved when the sugar solution in question is very dilute. Think watered down pop -- you know, when the cheapskate at the fast food joint packs as much ice as humanly possible into the cup before dispensing the soda. So, drinking lots of water during your meal may actually help spike your glucose levels. (although the stomach distension caused by the massive amount of water does wonders for limiting your capacity for food -- no room for that cheeseburger; my stomach is full of water)
honold said:
also heard about transfats, and the differences between saturated and unsaturated fats.
Anyone who has taken organic chemistry will know about the trans and cis positions of functional groups or atoms relative to a double bond. Food manufacturers saturate (hydrogenate) fats to make them more stable for cooking and storing. Unsaturated fats tend to go rancid more quickly and are thinner and runnier at room temperature, among other disadvantages. Unfortunately, the hydrogenation process creates "trans fats" by adding the two hydrogen atoms on opposite sides of the double bond instead of on the same side (cis) of the double bond as occurs in nature. This trans configuration causes the trans fat to interfere with lipid metabolism at least as much as saturated fats do (even if they are monounsaturated, which is what a lot of the partially hydrogenated polyunsaturates become).
Saturated fats interfere with lipid metabolism in a way that encourages formation of LDL (Low Density Lipoproteins). LDL is what people popularly (yet mistakenly) refer to as "the bad cholesterol" when they get their bloodwork back from the lab. LDL can also be thought of as those carriers which shuttle cholesterol away from the liver and into the bloodstream, ready for deposition onto arterial walls. HDL, often referred to as "the good cholesterol" can be thought of as those carriers which shuttle cholesterol back to the liver. It is dietary intake of saturated fat that largely raises serum cholesterol levels, NOT cholesterol, as people mistakenly believe.
Unsaturated fats (there are various degrees of unsaturation -- poly unsaturated... highly unsaturated in other words, and monounsaturated... lightly unsaturated, in other words) do not affect lipid metabolism negatively, so they are preferred in that way. In fact, polyunsatures may even reduce LDL levels and affect lipid metabolism in a positive way -- especially omega-3 polys. But there is a small caveat: polyunsaturates are easily oxidized and are more likely to form lipid free-radicals. Free-radicals, as you know, are nasty entities that can damage DNA -- in other words, they are carcinogens. Such is life; there is no such thing as a free ride. Antioxidants, however, like vitamin C, E, and Beta-carotene, can prevent oxidation and reduce the threat.
honold said:
my question is this: assume that i'm getting a perfect blend of requirements in terms of vitamins, protein, etc - a book-worthy balanced diet. assume this also happens 'magically'. if 100% of my calories were from fat, how would that change anything? comparing 1500 calories of a perfect diet vs 'automatic perfect diet balance' 1500 calories of pure fat.
First of all, that would be disgusting
Second of all, that wouldn't be too healthy. As I mentioned above, fats -- especially polyunsaturates -- can be carcinogenic. Add to that the amount of bile and other lipolytics you would need to digest all that fat, and that can't be good for your gall bladder. And what about the intestinal lube job? Things would go through you pretty quick. We're talking greased lightning here
Fat is good because it promotes CCK release, which is partly responsible for the feeling of satiety (the feeling of being satisfied, full... satisfied), as well as slowing digestion, but let's not go overboard here. They are also calorically dense, so it's easy to add calories unwittingly.
