Spend any time reading about, or talking to others about nutrition, muscle gain, and fat loss, and one word that you are sure to come across frequently is ‘insulin’. I thought I would put together an article, giving you the basics of what insulin is, what it does, and why it is important to maintain our physiology and make positive changes in body composition.
We will also have a brief chat about terms such as ‘insulin sensitivity, ‘carb sensitivity, and ‘nutrient partitioning.
Ok, so firstly, what is insulin?
Insulin is a hormone, produced by an organ called the pancreas. Remember, a hormone is a chemical produced by your body that sends messages to other parts of the body, resulting in an action at the target site’.
What does it do?
Insulin has a central role in regulating the metabolism, carbohydrates, proteins/amino acids, and fat within our body. It causes (amongst other actions) the following:
- The uptake of sugar (glucose) from our bloodstream into our muscles, liver, and fat tissue,
- Increased amino acid uptake into our cells; remember that protein is made up of lots of individual amino acids joined together,
- Increased protein synthesis; the making of new proteins within our body,
- Increased fat synthesis (the making of new fat in our body), and
- Decreased breakdown and utilisation of fats (decreased lipolysis).
Generally, our insulin levels rise in response to us eating carbohydrates. Most of you have probably heard of diabetes, which is primarily a disease of carbohydrate/glucose regulation in the body, in which insulin plays a vital part. For people with diabetes, their bodies either do not produce insulin or the insulin they are producing does not work very well.
Insulin sensitivity
This is a term that gets mentioned quite a lot these days, and rightly so; it is important! The term basically means how well the insulin in your body works; it is that simple. Generally, the leaner you are, the more ‘powerful’ your insulin is, and conversely, the less lean you are, the less powerful your insulin will be.
Insulin resistance
This is related to insulin sensitivity. Insulin resistance refers to when your body is in a state of poor insulin sensitivity; that is, your cells are resistant to the effects of insulin. This is also very closely related to the term ‘pre-diabetes’– in which patients are in a state of glucose and insulin metabolism that, if not corrected, will most likely lead to diabetes. In these situations, losing some body fat and improving food choices and timing is sometimes enough to prevent type 2 diabetes. You are probably starting to get the message that your glucose and insulin function is very heavily influenced by how lean you are!
Nutrient partitioning
This term sounds quite complex, however, think of it simply as the process of your body sending nutrients to certain places within your body. For example, the leaner you are, the better your body is at sending carbohydrates into your muscles, rather than into fat storage. Similar to insulin sensitivity, the opposite is true for those who are less lean.
This is part of the reason that as you get leaner and carry more muscle, you begin to require more carbohydrates to keep progressing. Have you ever noticed how, after a leg workout, your legs look full and muscular for the rest of the day? That is due to the soaking up all the available nutrients, and (with the aid of insulin) ordering them to be shuttled in there to start the recovery process.
Carbohydrate sensitivity/carbohydrate tolerance
This term is essentially describing how much insulin your body will produce in response to you eating carbohydrates. This is partly why two people with relatively similar body fat levels may respond differently to (and require), differing amounts of carbohydrates in their diet. We all know the people who can eat high energy carbs at almost all meals, and not suffer…. then there is the rest of us who start to get a little less lean if we consume too many high energy carbs outside the metabolic window.
So what does all this mean to us, and why does it matter in body transformation?
Well, quite simply, insulin is a key player when it comes to regulating body fat levels. Sure, there is a highly complex interplay between thyroid hormones, testosterone, oestrogen, cortisol, growth hormone, the list goes on, but insulin is the big daddy!
We know, nutrient timing plays a role in metabolic nutrition, and utilising nutrient timing protocols takes full advantage of insulin’s muscle-building potential while minimising its less than desirable effects. Intense exercise causes acute changes in our insulin function. These changes allow us to use nutrition to enhance recovery and increase protein synthesis (muscle building!) and decrease lipogenesis (the making of fat). This makes the metabolic window concept important. Avoiding high energy carbs outside the metabolic window can help keep our insulin levels quiet and stable, thereby allowing us to burn more fat, and gain more muscle!
