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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.
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