This is an amazing informative read. If you take the time to read through this article this is going to help you understand why you gain weight, loose weight, ramp up metabolism, slow down metabolism; but more importantly it's going to teach you how you can use what you learn to apply to your own life.
References
1. Reduced insulin secretion: an independent predictor of body weight gain. J Clin Endocrinol Metab. 1995 May;80(5):1571-6.
2. Acute postchallenge hyperinsulinemia predicts weight gain: a prospective study.Diabetes. 1997 Jun;46(6):1025-9.
We all know people who're extremely lean and muscular, who rarely gain fat even though they eat like horses. We also know people who eat like birds, only to struggle with fat loss and body composition.
What's the big difference between them?
How is it that some people manage to get fatter even while eating light?
I'll tell you. The difference is that the lean group has better nutrient partitioning. In other words, they're able to easily shuttle ingested calories away from fat stores, and direct them into muscle. Pretty simple, but let me explain anyway.
When you're in caloric excess, calories can either go into muscle or fat. When dieting, calories can either be pulled out of fat or they can be pulled out of muscle. Someone with good partitioning and a high metabolic rate is easily able to pull and utilize energy from fat, and direct energy into muscle.
So it follows that if we want to be maximize body composition, we should really be after maximizing this process for ourselves.
Internal Signaling vs. External Output
I often tell people that instead of focusing so much on external things, like how many calories they burn and how much they eat, they should think a little bit about how their body is working from the inside out.
The reason some sixteen-year-olds can eat two pizzas a day, wash them down with a half-gallon of Coke, and still be lean and muscular is because their internal signaling for a good body overpowers the junk they're putting into it.
People with good internal signaling can eat all the pizza they want and still look good.
What's the difference between them and you, and what if we could get your body to function like their bodies? That's what this series of articles is about.
Hormones and Neurotransmitters
The process of partitioning is largely controlled by hormones and neurotransmitters. We have quite a bit of control over some of these, but not a lot over others.
A hormone is really just a chemical messenger that sends messages. Your body has an assortment of these messengers floating around. The ones we're concerned with send messages that "tell" your body to increase or decrease fat burning, or either increase or decrease muscle building.
These hormones have a profound effect on how easily you gain or lose fat, how easily you gain and lose muscle, your metabolic rate, and whether the food you eat ends up as muscle or fat. Your lifestyle, diet and exercise habits, in turn, have a profound effect on these hormones.
Some of the main hormones involved in muscle growth and fat loss are insulin, glucagon, testosterone, growth hormone, IGF-1, thyroid, epinephrine, estrogen, cortisol, and even neurotransmitters like dopamine, serotonin, and GABA.
Insulin and glucagon
One of the most important factors in determining nutrient partitioning is your ratio of insulin to glucagon. Insulin and glucagon levels are most strongly influenced by diet, so we can exert great control over them through our eating habits.
Insulin and glucagon are both released by the pancreas. The job of insulin is to lower blood sugar by causing cells to open up and receive nutrients. It acts to transport glucose and amino acids into cells. Thus, insulin is a powerful growth stimulator.
The most powerful stimulator of insulin is carbohydrate intake. The only carbohydrate that doesn't affect insulin is fructose.
Glucagon has the opposite actions of insulin. It's a mobilizer. It raises blood sugar by moving glucose and amino acids out of cells and into the bloodstream when blood sugar gets too low.
These two pancreatic hormones work in balance to provide relatively stable levels of blood glucose to ensure that the brain doesn't run out of fuel.
Insulin 101
Let's talk about insulin. It's great for growth, but unfortunately, it's indiscriminate in whether it causes nutrients to be taken up by muscle cells or fat cells — so you want to learn to manage it and manage it well!
Jacking insulin too high at inopportune times is a good way to get fat. How much insulin your body responds to from a given glucose load is determined by three things:
1. How fast the glucose enters the bloodstream.
2. How sensitive your muscles are to the insulin.
3. Individual hypersensitivity to glucose: how much insulin your body secretes in response to the appearance of a given amount of glucose in the bloodstream.
The speed at which the glucose enters the bloodstream is normally controlled by the type of carbs you consume. Fast carbs are simple sugars like dextrose or sucrose. Slow carbs are complex carbs like oatmeal and fibrous veggies.
It's also influenced by what else you eat with your carbs. Having a little fat slows the glucose release into the bloodstream.
Slow carbs.
Fast carbs.
Insulin sensitivity could be thought of as how well your muscles soak up glucose in response to a given amount of insulin. This is highly variable and can vary almost tenfold among people at the same body-fat percentage for genetic reasons, as well as due to the impact of exercise and diet.
Both resistance training and cardiovascular training improve insulin sensitivity, but probably the most important factor is weight gain or loss. Weight loss tends to improve it and weight gain to decrease it.
Those with overall good insulin sensitivity would store more nutrients with a given amount of insulin than those with poor insulin sensitivity. We often hear that having good insulin sensitivity is always a positive thing; however, that's not necessarily true.
Obesity is associated with whole body insulin insensitivity, (also called insulin resistance), but it appears the reduced tolerance comes about as an adaptation as the body tries to avoid further fat gain because it simply doesn't want to store any more nutrients.
Having very good insulin sensitivity has actually been seen as an independent predictor of body weight gain (1).This makes sense when you think about it from a survival and set-point perspective.
Insulin is a storage hormone. Increased insulin sensitivity means easier nutrient storage. Decreased insulin sensitivity means decreased nutrient storage.
When would your body normally want to store a lot of nutrients? When it thinks it's starving or when it thinks a famine is imminent. Insulin resistance can actually be looked at as a way the body tries to spend excess nutrients. Instead of getting stored, nutrients float around in the bloodstream waiting to get burned off.
Think of how easily obese people lose fat when they start exercising. Losses of over a pound of fat per day are not uncommon. This is partly on account of insulin resistance. Insulin-resistant people eat a meal and their blood sugar and insulin stay elevated for hours!
Having these chronically high insulin levels also increases central nervous system insulin signaling, which helps suppress food intake and offers resistance to further weight gain. Problems arise when individuals continue flooding the body with excessive amounts of food even though they already have excessive nutrients floating around in the bloodstream.
First, the liver grows insulin resistant. Then the same thing happens to the muscles. Finally, fat cells grow insulin resistant. Eventually there's no place to store any more nutrients, the pancreas wears out and no longer releases any insulin, and full blown diabetes sets in.
What we really want out of insulin (from an overall body composition management perspective) is to be quite insulin-sensitive in the muscles, and not so sensitive in fat cells. From this end, exercise is the most important partitioner of all as it selectively enhances muscle cell insulin sensitivity at the expense of fat cell sensitivity.
That means if we eat the majority of our higher carb meals close to training, we selectively partition nutrients towards muscle and away from fat.
Meal timing also has a big relevance. Unless you train in the evening, it's a good idea to avoid nighttime meals high in carbs, as muscle glucose tolerance is significantly impaired compared to in the morning.
Supplements like fish oil and magnesium also make the muscle more insulin sensitive. I recommend a minimum of 6 grams of fish oil per day and 300 mg of magnesium. Magnesium forms that end in an "ate," like magnesium aspartate, are more bioavailable.
The high-quality fish oil in Flameout and magnesium aspartate in ZMA help muscle become more insulin-sensitive.
Glucose hypersensitivity
Having mentioned insulin sensitivity, probably the best predictor of future fat gain is the amount of early phase insulin release in response to a given glucose load, or what I like to call glucose hypersensitivity (2).
Glucose hypersensitivity is not something really talked about in the fitness world, but I believe it's the most important factor related to insulin or blood sugar from a body composition perspective.
Some people have metabolisms that are extremely reactive. Their bodies tend to respond with a lot of insulin in response to any amount of carbohydrate. This occurs even if they are sensitive to that insulin.
Their blood sugar swings up, but just as quickly it swings back down, and they tend to get hypoglycemic. They eat a meal and an hour later they're starving again.
This probably occurs for similar reasons that some people are very insulin-sensitive. The body or brain thinks a famine is imminent and it's something the body does to ensure that all incoming nutrients are stored as efficiently as possible. The brain freaks out when it sees glucose in the bloodstream. It wants to ensure that all nutrients are stored as efficiently as possible, so it overcompensates by releasing a little too much insulin.
In the same study mentioned above, 107 people were divided up into four groups based on how much insulin they secreted to a given glucose load and their insulin sensitivity. They were then tracked for fat gain over a 16-year period of time.
GroupYearly Fat Gain:
A: Low acute insulin secretion with good insulin sensitivity
176 grams per year
B: Low acute insulin secretion with poor insulin sensitivity
152 grams per year
C: High acute insulin secretion with poor insulin sensitivity
271 grams per year
D: High acute insulin secretion with good insulin sensitivity
672 grams per year
As you can see, the group with high glucose sensitivity and good insulin sensitivity actually gained almost three times as much fat per year as any other group!
Unfortunately, the metabolic functioning of many figure competitors probably more closely resembles this group than any other. They have good insulin sensitivity but are also hyper-reactive. This is especially true when dieting.
Ironically, the metabolic function of figure athletes probably makes them most susceptible to fat gain.
Glucose hypersensitivity tends to correlate with acquired leanness. For reasons which will be discussed in more detail in a later article, this is partly why it's so difficult to maintain an ultra lean state for long.
Problems with excessive glucose reactivity are almost always associated with hypoglycemia. If you tend toward hypoglycemia you should take steps to ensure the slow release of insulin into the bloodstream.
This is what I'd recommend:
A: Stay away from simple sugars with the exception of post-workout. Get your daily carbs from starchy or fibrous sources.
B: Have protein with each meal. Protein also stimulates the release of insulin, but it's balanced out by the additional release of glucagon.
C: Have fat or fibrous veggies with each meal. Both fat and fiber slow gastric emptying.
D: Don't snack on carbs alone, ever.
E: Stimulate! As long as you exercise, don't be afraid of having some caffeine or other mild stimulants throughout the day.
Stimulants blunt insulin sensitivity in both fat and muscle cells, but if you exercise, you selectively increase muscle insulin sensitivity. Combine them together and you get reduced fat cell insulin sensitivity and enhanced muscle cell insulin sensitivity.
F: Gain some weight! Yes, you heard me right.
Glucose hypersensitivity tends to correlate with leanness. It can occur if you're trying to hold a condition that's excessively lean for you and will often go away just by going up in body-fat a couple of percentage points.
In the next installment, I'll talk about maximizing your insulin to glucagon ratio, the myth of cortisol, and how to take advantage of the most powerful fat burner of all, epinephrine. - Jen Heath - ACSM Certified Personal Trainer
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Tom - Independent Team Beachbody Coach
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