Insulin Index - Carbs Not Just Carbs

CARBS AND FATS ARE DIFFERENT IN TERMS OF INSULIN

A Carbohydrate Is Not Just A Carbohydrate
In this section, we'd like to demonstrate that not all carbohydrates were created equal. Specifically, we will be discussing a few key areas:

1. The insulin index vs. the glycaemic index

2. The superiority of low-GI and II diets

3. The difference between liquid carbohydrates

While older carbohydrate classification schemes were centered on the notion of simple vs. complex carbohydrates (a structural classification), newer schemes focus more appropriately on the absorption profiles (glycaemic index) and physiological effects (insulin index) of these carbohydrates (a functional classification). Hopefully if you have read this far, you will know this to be true. And it is almost definite that in years to come there will be further advances into the understandings of food metabolism and the effect they have on your health and appearance. Research athletes and trainers are hungry and ready to receive.

Ludwig et al (2000) described the following list of benefits for eating a low GI diet:

• Better nutrition (better micronutrient profile and more fiber)

• Increased satiety

• Decreased hunger

• Lower subsequent energy intake (second meal effect)

• Fat loss

• Better fasted insulin and glucose

In a study by Agus et al (2000), it was demonstrated that during a short, 6 day, low-calorie diet, a low-GI carb intake preserved metabolism and enhanced fat loss vs. a high-GI diet. The low GI group saw a 5% decline in metabolic rate and a 7.7lb weight loss while the high-GI group saw an 11% decline in metabolic rate and a 6.6lb weight loss. In these subjects, fasted glucose and insulin values were lower in the low-GI group, indicating better glucose and insulin sensitivity. So we know that the glycaemic index has very important uses and correlates well, most of the time, with improvements to your health and physique and your insulin when used accordingly.

Spieth et al (2000) and Ludwig et al (2000) showed that 4 months of low-GI eating was superior to 4 months of high-GI eating in overweight teens. The low-GI group lost 1.5 points on the BMI scale and 2.2 lbs while the high-GI group gained 2.88lbs and increased their BMI. In addition, these studies showed that a low GI meal reduced food intake during subsequent meals while the high GI meal lead to overeating. This is of course because higher fibre and lower GI diets naturally suppress appetite by making one feel full up.

Finally, Pawlak et al (2001) showed that in rats, a low-GI diet led to decreased fasting insulin and glucose values, decreased fat mass, and decreased insulin and glucose values during a glucose tolerance test. Therefore, body comp as well as glucose and insulin sensitivity improved.

The bottom line here is that when all else is equal, a diet containing mostly low-GI carbohydrates is superior to a high-GI diet for losing fat, preserving metabolic rate, and maintaining healthy insulin sensitivity and glucose tolerance. So people have been following good advice for many years. Now with research into the insulin index become popularised you can see how eating accordingly to maintaing healthy insulin levels is even more beneficial, and the odd foods are highlighted that do not correspond on both scales, such as milk.

Next, we'd like to illustrate the differences between popular liquid carbohydrates including maltodextrin, dextrose, fructose, and sucrose. As here, there is much confusion as to how they affect blood glucose and insulin levels, especially with their impact on your training efforts.

Maltodextrin is a glucose polymer (a string of glucose units put together, similar to the protein peptide). It is therefore, by definition, a complex carbohydrate. However it's more complex nature does NOT slow digestion. Therefore, the GI and II remain high. Maltodextrin is the absolute best carbohydrate to consume during exercise for rapidly delivering blood glucose and for muscle glycogen recovery. It's also best for fluid uptake.

Dextrose (glucose) is a simple carbohydrate unit (similar to the amino acid). While it's good for exercise situations (malto is better), you're probably better off adding some dextrose to your maltodextrin formula. A little bit of dextrose may enhance the already excellent fluid uptake that occurs with maltodextrin during exercise.

Fructose is a simple carbohydrate unit, but it's structurally different from glucose. Due to its structure, it can possibly cause GI problems and/or decrease fluid uptake with exercise. Fructose, unlike other simple carbs, has to be "treated" in the liver and it reaches the muscle slowly.

Finally, sucrose consists of glucose and fructose units bonded together. Therefore, upon digestion, you get glucose and fructose in the GI (and the benefits and consequences of each).

Based on three studies reviewed (Blom et al 1987, ven Den Burgh et al 1996, Piehl et al 2000), it appears that dextrose is 72% faster than fructose for muscle glycogen resynthesis . As a result, at the end of 8 hours, muscle glycogen was 30% higher with dextrose ingestion. However, in another study, at the end of 4 hours, muscle glycogen was 15% higher with maltodextrin ingestion vs. dextrose. So bottomline is that dextrose is superior to fructose, although malto beats dextrose hands down generally..

A Fat Is Not A Fat

In this section, I'd like to demonstrate that not all fats were created equal. Specifically, I'll briefly discuss:

1. Fat Structure - Fatty Acid Chains and TGs

2. MCTs - Medium Chain Triglycerides

3. Olive Oil - Monounsaturated Fatty Acids

4. CLA - Polyunsaturated Fatty Acids

5. Fish Oil - Omega 3 Polyunsaturated Fatty Acids

There are three different types of fatty acids; saturated (coming from animal fats), monounsaturated (coming from olive oil and avocados), and polyunsaturated (coming from flax oil, hemp oil, fish oil, canola oil, safflower oil, etc). Dietary fat, rather than simply floating around as free fatty acids, typically is packaged up in the form of a triglyceride. Basically, a triglyceride consists of 3 fatty acids (usually all of the same type) bound together by a glycerol backbone. Essentially, the glycerol backbone has 3 carbons and a fatty acid is attached (via a dehydration/synthesis reaction) to each of the 3 carbons.

Based on this structural phenomenon, scientists have recently begun exploring an interesting development in fat science. They've begun making "structured lipids." In essence what they're doing is making diacylglyerols (2 of the carbons have fatty acids attached while 1 does not) and special triacylglycerols (where there are fats of different lengths and properties attached to each carbon).

In clinical studies, these structured lipids have been shown to increase protein synthesis in patients suffering from wasting. In addition, these fats are easily oxidized (like the long chain fatty acids in fish oil) which leads to a thermogenic response rather than a storage response. As a result these structured lipids are now being heavily studied. While they're not on shelves yet, it wouldn't be surprising if these structured lipids become food additives in the near future.

MCT's and CLA, probably due to their early introduction to the weightlifting scene and the huge media hype associated with this introduction, have gotten a bad reputation. These fats may, in fact, assist in weight loss.

MCT's, due to their medium chain length, are easily oxidized by skeletal muscle. This is due to the fact that MCT's are quickly and easily transported to the fat furnace, the mitochondrion. As a result, research (Hill et al 1989) has demonstrated that TEF (thermogenic effect) with MCTs is double that of other fats, making it comparable to protein in this regard.

CLA has remained a relative mystery to the research community. This is probably due to the various forms (isomers) of CLA. Regardless, some research (Blankson et al 2000) has shown that 12 weeks of CLA supplementation (at doses above 3.4g/day) can increase LBM and decrease fat mass vs. olive oil. While the olive oil group gained 1.5 lbs of fat and no lean body mass, the CLA group lost 4.5 lbs of fat and gained 3 lbs of LBM.

Speaking of olive oil, even this "good fat" is better than saturated fat for body composition. In a study comparing safflower oil, beef fat, palm fat, and olive oil, it was shown that olive oil leads to a 14% higher oxygen consumption rate than the other fats.

Delarue et al (1996) showed that fish oil supplementation (6g/day added to the diet) dramatically changed the metabolism of fats and carbohydrates.

During an OGTT (oral glucose tolerance test - drinking a big 75g whack of liquid sugar and measuring the subjects for 2 hours afterward), the fish oil group burned 27g of fat vs. 20g in the placebo group. The fish oil group also burned 28g or carbs while storing 36g and the placebo group burned 51g of carbs while storing only 14g.

In addition, baseline insulin was 30% lower in fish oil group and insulin responses to OGTT were 50% lower in the fish oil group. What this tells us is that fish oil allows the body to burn more fat and store more muscle glycogen, repartitioning fuel away from fat cells toward muscle cells.

Since fish oils are polyunsaturated fats, it's important to not only increase fish-oil intake, it's important to shift the ratio of polyunsaturated fat to saturated fat (P/S). Van Marken, Lichtenbelt et al (1997) showed that the polyunsaturated fat to saturated fat ratio is important to metabolic rate. A higher ratio of P/S leads to metabolic increases (22% increase in TEF and 3% increase in daily RMR).

So, if there's one thing you need to take from this discussion, all else being equal, the fat composition (not just total intake) of your diet is very important to your body composition. Saturated fats, while necessary to a small extent, should only make up a small part of your diet while other fats like olive oil, fish oil, flax oil, MCTs, and CLA all have a place on your plate. This way you can get the same amount of daily energy from fats while gaining lean mass and without gaining body fat.

Choosing Your Food Wisely

Hopefully, by reading the above scientific data and research you can see that, in terms of your body composition and health, and the results that you obtain long term from your training, is not just to do with energy intake in total, rather that energy intake is important, alongside energy balance, and smart macronutrient choices.