Human Biochemistry, the basics as relating to dieting.

[thorfinn]

Some of you have probably seen this before in other fora, and I've mean to post it up here for a while, but hadn't summoned enough round tuits. A reasonable chunk of my audience here are quite aware of this stuff already, but there's also plenty who aren't. If you're one of the former, feel free to drop corrections in if any are spotted. And if

Comments

[wildilocks]

Interesting. I've found the most effective wieght loss to come from eating a low-carbhoydrate diet, because your body usually will send you "false" hunger pangs after eating too many carbohydrates, resulting in a very bad cycle of eat crap, feel hungry, eat more crap, gain weight!

I also have in the last 6 months achieved an excellent level of fitness from 2-3 sessions of 1 1/2 hours per week of high intensity cardio workout, and I'm pretty sure I've been mostly eating more, but not putting on extra weight in that time. While you say that anaerobic exercise reduces your metabolic rate for hours afterward, I was always udner the impression that regular higher-intensity workouts raised you BMR overall. Yes or no?

[thorfinn]

"High-intensity" does not necessarily mean "anaerobic". The term literally means "without air" - i.e. your body is burning glucose without using oxygen. Sprinting is so energy intensive that after the first second or so, more energy is needed than there is oxygen to burn, resulting in anaerobic exercise. "Aerobics" is about the level of exercise where almost all the exercise is "aerobic", hence the name. It does teeter a bit on the border between - but that's the idea. The point of "aerobics" is to maximise the amount of exercise that you're doing without getting into anaerobic metabolism. That's not necessarily a point that your particular instructor actually understands, but it's certainly the original reason for the name

Thanks for the info

[velvet_wood]

I found it very interesting, especially as I'm in the process of deciding on a diet and exercise program right now. Things get complicated for me because I have fibromyalgia, and any sort of even vaguely non-gentle exercise leaves me too tired and hurting to move. I had noticed, though, that while I might can only do 5 minutes of fast exercise, that slow, strengthening exercise such as weight-training or yoga does _not_ seem to hurt me nearly as badly, even if I'm doing quite a bit of it. So basically, five minutes of sweating and panting will have me cramped up and collapsing, but fifty minutes of steady, gentle effort won't. From what you've described, this seems to just be an exageration of a normal reaction, rather than something totally unheard of.

Opinions on carb-restricted or low-glycemic index diets? Those are what I'm looking at right now, primarily because they tend to make me feel better and have more energy rather than making me feel exhausted and sick.

Velvet

Re: Thanks for the info

[thorfinn]

One of the things that's fairly clear about fibromyalgia is that there is something distinctly odd going on with metabolic biochemistry. It feels to me (and this is an untested personal opinion) like there is something broken in the glycogen to glucose conversion pathway, resulting in the primary energy pathway being amino acid metabolism (hence the increased nitrogen byproducts of various kinds), instead of more normal glucose metabolism.

The result of that is what you describe - carbohydrate metabolism wouldn't do as much for you as for someone with "normal" biochemistry, because your body mostly isn't burning carbohydrates very well. What also matches is that fast exercise requires glycogen to glucose metabolism, because nothing else produces energy fast enough... Whilst slow exercise can make do with other sorts of metabolism.

What my answer is really boils down to, though, is try it and see. If you genuinely do feel better on a low-GI, higher protein, diet, then it is likely better for you. And definitely stick with gentle

[australian_joe]

Useful to have it all collected in one place like that, and in places you've extended my knowledge.

I have a question, if this is something you know about :

Your body burns protein (i.e., muscle tissue) in preference to fats!

I've always thought that the amino acids L-Carnitine (and the related Acetyl-L-Carnitine) altered that balance, to the point where stored fats were promoted in terms of at which point they were used. Used in combination with CoQ10, I've been told the effect is that muscles are spared and that further energy demands would be fueled preferentially from fat rather than muscle? Have I misunderstood?

[thorfinn]

I suspect there are things that can change that balance (presumably by messing with the concentrations of co-factors that promote the different steps)... But, bear in mind that the body has further regulatory mechanisms to bring those things back into balance. Biochemistry is a very complicated dance of multi-way dynamic equilibria, and a swing in one direction typically results in swings elsewhere.

So - what you're describing is possible, but I don't know off hand without doing plenty more research. Personally, I'd go with relying on my body's actual mechanisms, and keeping the gentle exercise on, the protein intake up, and reducing the amount of carbs I eat, as well as keeping fats down to a non-crazy level.

[elindal]

Thank you for that.

Now all I need is someone to tell me how to override the hunger urge. The medication I am on makes me constantly hungry, even when I know I don't need to eat (like when I have just gorged myself at Squire's Loft). The brain can tell the status of the bloodstream, but certain things can screw it up. :(

I will walk more - I promise.

[thorfinn]

Glerk! You're probably in a situation where you do need to calorie count. If your brain mechanism in control of that is screwed, then you've got no option apart from actually doing the numbers. I'm told that you do get quite adept at estimations and suchlike once you've been doing it for a while... just remember that you need to track fat, protein, and carbs separately.

[thorfinn]

Further to my previous reply, simonb has mentioned http://www.fitday.com which looks like a good way to get started with counting.

[qamar]

Fitday is great, especially for a nutritional breakdown of food to see where various vitamins are in abundance and which are lacking.

[halloranelder]

Thank you. It even makes sense!

[thorfinn]

That's what I was aiming for. Good o.

The first diet that is actually working for me...

[domesticmouse]

After many years of trying to lose weight, I finally had one shoved in my face - Potatoes not Prozac. What the book basically covers is that some of us are actually hyper sensitive to sugar, i.e. everything from sucrose, fine milled white flour (think french bread), to beer. She found this sensitivity was particularly prevalent in alcoholics and children thereof.

I know I'm sounding like a salesman, but if anyone here is having trouble with food, go grab that book. It's on the shelves at about $20. It has made me a lot happier... (Being sugar low induces grumpiness in a major way... ;-)

Re: The first diet that is actually working for me...

[thorfinn]

Yeps. The biggest irony with "diet" foods, is that they are generally zero fat, but 50% sugar, and the rest is relatively simple carbohydrate. That's the worst thing you can eat if you're trying to diet... because excess glucose in the bloodstream is used to make glycogen, but there's only so much glycogen the body can store... and the rest is used to make fat!