Monday, May 9, 2011

The Dizzying World of Dieting

I received a really interesting series of questions from a good friend of mine today. A common friend of ours had adopted a low-carb diet with apparently great results, and now my friend has a bunch of questions, largely concerning how insulin relates to our bodies' metabolism. I nearly started hyperventilating from the prospect of a captive audience interested in biochemistry ;)

Specifically, my friend had been directed to an author, whose main thesis is...well I can't seem to find a coherent thesis to summarize his post, but I want to make a few observations about it.

I will confess that he articulates a lot of potentially difficult information in a way that any reader can understand. He's good at providing real world analogies, and he uses descriptive terms and simple ideas that summarize his points well. The world can definitely use more people who are good at making these things easier to understand. Also, the basic physiological and biochemical ideas he's describing are pretty sound.


He rambles, a lot (I admit, I'm just as bad), and took a billion words to state the same concept a million different ways. He also has an odd habit of standing up for fat people who are undeservedly maligned, while in the same post accusing people who don't agree with his views of being fat and ignorant. wtf?

Most importantly, this guy is basically saying that he's solved the problem of overweight/obesity. Trust me, people, if someone ever tells you that they know the answer to a question that has been plaguing science for decades, feel free to pat them on the head and go find an adult to talk to. This is probably not a problem that's going to have a simple solution. Even if it does, you're not going to find it on some guy's blog--even if he's an MD. After all, I'll be an MD in two weeks, and sometimes I wear my shirt inside out without realizing it. LAWL

SO! What were those questions my friend (let's call him Tim) was asking? They are thusly:
1. How does fat get stored in our cells? Is it indeed insulin which triggers it?
2. Given 1, Is it true that even if there is fat available in the bloodstream, it won't be stored in our body without insulin? (ie without insulin, the body will flush out the excess fat without storing it)
3. What is insulin resistance?
4. Does insulin resistance actually affect liver cells before other cells? And does our liver actually secrete sugar into the bloodstream?
5. Does consumption of sugar and carbohydrates trigger an increased production of insulin?
6. Do obese people tend to have elevated insulin levels? (even when not eating)
7. Does glucagon actually counteract the effect of insulin?
8. Given 7, and given the rest of the low carb theory, why can't an injection (or pill) be created for glucagon to be administered after eating? That way as I understand (in my limited reading), wouldn't insulin levels reduce, allowing the body to consume the stored fat, providing energy between meals?

Amazing. Delicious. The thought of answering these questions makes me salivate. Let's dig in.

We need to start with a very cursory overview of basic nutrition. Our energy comes from 3 different macronutrients: carbohydrates, fat, and protein. Carbohydrates are sugars of varying complexity. You can make complex carbohydrates from combinations of the basic sugars. The fundamental basic carbohydrate in the human body is glucose. Fructose is another basic carb. A glucose molecule attached to a fructose molecule makes sucrose. Glycogen (which is almost the same thing as starch) is a huge molecule of hundreds of glucose molecules attached together. Glucose is stored as glycogen in the liver. Fats consist of different types of fatty acid chains and are stored in adipose (fat) tissue. Protein is made up from amino acids, and is the major structural component of all our cells, including muscle. The body can bascially turn any macronutrient into either of the other two (except certain amino acids, which we can't make on our own).

Questions 1, 2, 4, 5, and 7 can all be answered this way: yes. lol. To be more specific, refer to the image with all the blobby stuff. Basically, in fasting states, when you're hungry and your blood sugar is low, the pancreas releases a hormone called glucagon. This acts on the liver to release stored sugar and to create new sugar from scratch. That way, you don't die in between meals. Evolution win!

In "fed" states, after you've consumed a meal, your blood gets flooded with all the sugars from the food you ate. Blood glucose levels rise, which tones down glucagon and turns up insulin. Insulin promotes sugar uptake into the liver (and all cells, really) for storage, and promotes fat intake and storage in fat cells. Your body is always producing both insulin and glucagon, but their levels are balanced so as to keep your blood glucose levels at a constant level. (NB question 2 will be discussed in more detail with question 8 at the end of the post.)

Questions 3 and 6 get a little more complicated. It is based on a cellular molecular process called down-regulation. It's a negative-feedback process. The best example would be topical nasal decongestants. When someone is suffering from allergies, the blood vessels in the membranes of their nose get "leaky". Fluid seeps out and drains out the nose, producing some of the symptoms of allergy. Nasal decongestants work by spraying a drug into your nose that constricts the nasal blood vessels and stops the leaking. BUT! If you continue to use the spray regularly for a few days, the cells in the blood vessels get tired of being bombarded with drug. They then start to get rid of the receptors on their cell surface that bind the drug. So you end up needing more of the drug to get the same effect!

Insulin works the same way, but the response is much slower--it takes years, rather than just days. People who run their blood sugars high all the time (presumably by eating too much unhealthy food) have constitutively high levels of insulin in their blood. Eventually, the cells in their body get sick of listening to insulin's constant nagging, and they stop listening--by decreasing the expression of insulin receptors, so the insulin has less effect. So the body has to produce more insulin to keep glucose levels under control. Which leads to more down-regulation of insulin receptors. Eventually, the body can no longer produce enough insulin to keep up, and glucose levels go through the roof, leading to increased risk of cardiovascular disease, kidney failure, and blindness. This process is referred to as Type II Diabetes Mellitus, and it's one of the biggest medical problems facing our society today.

Questions 2 and 8 are sort of plausible/true in theory, but impractical for a number of reasons. Low insulin levels lead to high glucose levels, which is a trigger for insulin release. The only way to avoid a compensatory surge in insulin is by having a defective pancreas that can't produce insulin. Unfortunately, that's the pathological basis for Type I Diabetes Mellitus. People who can't make insulin get impossibly high blood levels of glucose, but the glucose can't get into their cells, so they actually think they're starving. This causes the body to synthesize ketones from stored fat, which eventually turns the blood to acid and causes death. :(

Conversely, giving a person an injection of glucagon might indeed lower their insulin levels, but it will still cause an increase in blood glucose levels. That's the stuff that leads to the cardiovascular disease and kidney failure and blindness :(

Now, the whole point of all these questions, I think, is probably related to the very common question: will the Atkins diet make me look like Megan Fox? I've done a little research into it, and I'd like to write about it, but I did promise my fiancé I'd clean the bathroom today. So let me get to that, and I'll see if I can extrapolate some of this sciencey stuff into practical stuff later.


G said...

When Tim told me you were going to answer some questions for him, I was excited. Thanks for posting this Chris.

I don't much to add about the article: your answers are good, and I sent the article to Tim mainly because it summarized the book. I had sent him an article on sugar written by Gary Taubes, author of that book. The link is at the bottom.

Instead, I'll describe how I've been eating. It might give you something to work with for your next post.

I wouldn't say I eat particularly low carb. I eat what's called a paleo diet. What that is depends on whom you're speaking to, it's more of a philosophy. The basic idea is avoiding many neolithic foods which seem to cause digestive problems. I tend to eat:

- lots of meat and eggs.
- lots of vegetables
- lots of fermented foods such as Kimchi, sauerkraut, kefir, yogurt
- some higher fat or aged dairy, such as cream or cheese
- some starches: I eat a lot of sweet potatoes.
- coconut oil for cooking
- olive oil and balsamic vinegar for salads
- some fruit and some nuts
- wine, dark chocolate or spirits

I'm not eating: wheat, rice, corn, soy, legumes, sugar and industrially processed foods.

(I did not eat much rice, corn, soy or legumes before, either)

It may have been lower carb when I described it to Tim a few months ago, but I'm much happier since I added in sweet potatoes. I wasn't really consistent with it until I added those; I think I had too few carbs and would switch to "regular" eating. I typed in a few days meals in a food calculator, I'd estimate I'm eating about 20-30% carbs.

I believe that broad macronutrient categories can be deceptive. I think I'd feel much different if I had 20% of my calories as fructose. Another big element is reducing intake of omega 6 PUFAs, as they work against omega 3's.

A big emphasis of this eating style (the term diet doesn't seem right) is food quality. I get grass fed beef from a local farmer, and eggs from chickens which live outside. It's easy to tell the difference: the yolks are bright orange, firmer, and they taste great.

I had been eating this way off and on for a few months, but started in earnest a couple of weeks ago once I finished a weight lifting program (gained about 5 pounds of lean mass in a month with 30 mins per week in the gym, but that's another story). I can report some preliminary results.

- total disappearance of dental plaque
- lack of fatigue (I used to get tired after meals)
- Generally no indigestion
- Much greater satiety. Hunger feels different; it's never very urgent. I feel contented and energetic throughout the day, and can eat hours later than normal without thinking twice.
- fairly rapid weight loss of a couple of pounds of fat gained while weight lifting.

I have made no conscious effort to restrict calories. I just eat until I'm full yet seem to be losing weight. I think satiety is a big part of it. I could easily eat 1500 calories of junk food. It is very hard to eat 1500 calories of meat and vegetables.

All of this only amounts to a sample of one. It's also only been a few weeks, though I'd noticed these effects to varying degrees even when only eating this way partially.

I'm well aware it's impossible to figure out exactly what caused those results, or disentangle any placebo effects. But I don't think it's all placebo, unless I can will plaque to disappear and my stomach to shrink.

I view it as an ongoing experiment. In a few weeks I will try incorporating bread from a baker (to avoid the added glucose/fructose + processed ingredients confounder) and see what happens. If I had to bet, I would guess that the lack of industrial foods is the biggest factor.

p.s. Funny you mentioned Megan Fox. According to this she got to look like Megan Fox by eating a Paleo diet:

G said...

Also, Tim asks good questions.