Should we eat based on food indexes?

A short while ago, I did a post on insulin and body fat (Insulin, Body Fat and You). As I pointed out in that post, among insulin’s many roles is that it serves as a pro-storage hormone that promotes the formation of new tissue.

Whenever you eat foods that provokes a substantial insulin release from your pancreas, your body is signaled to build either fat,  muscle or both. Obviously, the more structured resistance training you follow and the better you time your insulin spikes, the better able you are to use insulin’s mass building effects for muscle growth and not fat. Sadly, the common eating pattern in North America is to eat insulin producing foods without much foresight, which is part of the reason we battle the bulge.

Wild swings in insulin also tend to provoke increased hunger, which is not good if you are trying to control intake and by extension, body weight. I think it goes without saying that teaching people how to avoid crazy swings in insulin is a good thing.

In the 1980’s, David Jenkins from The University of Toronto, was the first to quantify how quickly food is digested and raises blood sugar. His system became known as the glycemic index (GI).

The creation of the glycemic index was a quantum leap forward in highlighting how seemingly similar foods can have wildly different biochemical properties in our bodies. In fact, the GI was such a popular and powerful idea that it spawned an entire series of diet books and programs, books that still can be found in bookstores today.

Unfortunately, subsequent research has shown us that are several major problems with basing food choices solely off the glycemic index. One of the major problems is that the glycemic index was derived studying foods in isolation. In reality, we typically eat mix-meals which throws off the GI readings.

Additionally, the method of food preparation and cooking can change the GI of a particular food. I spoke at a conference recently and one of my fellow presenters, Dr. Lonnie Lowery,  delivered an excellent talk on food preparation. He pointed out that if you freeze, then toast, white bread you can dramatically lower its GI. Keep in mind I still don’t think this makes white bread a particularly healthy choice, but it’s still neat to see how cooking can change the properties of our foods.

However, the biggest shortcoming of the GI is that it does not account for typical serving sizes. You see, in order to standardize the measure, the glycemic index is based on a representative serving size of 50 grams of the food in question. Sadly, this has caused some high glycemic index foods (i.e. carrots, watermelon) that aren’t typically eaten in 50 gram quantities, to still struggle to shed their “foods to avoid” label anti-GI zealots.

To address this shortcoming, later research suggested the concept of glycemic load (GL), which is just a function of the GI of a particular food x typical serving size.

As we can see in the table below, many of the moderate/high glycemic index vegetables and fruits actually have a low glycemic load, whereas most cereals and grains (with the exception of high fiber cereals like All Bran), have quite a bit higher glycemic load.

Perfect. For anyone wanting to avoid insulin surges and control body fat it’s case closed, right? Just eat low glycemic load foods…

Errr, not exactly.

It turns out that although glycemic load is highly correlated to insulin release, there are several low glycemic foods that can cause remarkably high insulin surges. These foods may or may not need to be avoided by insulin resistant individuals who are trying control body fat.

Insulin Index (downloadable sheet)

Food Glycemic Score Insulin Score
BREAKFAST CEREALS
All-Bran 40 32
Porridge (Oatmeal) 60 40
Muesli 60 40
Special K 70 66
Honeysmacks 60 67
Sustain 66 71
Cornflakes 76 75
CARBOHYDRATE-RICH FOODS
White pasta 46 40
Brown pasta 68 40
Grain [rye] bread 60 56
Brown rice 104 62
French fries 71 74
White rice 110 79
Whole-meal bread 97 96
White bread 100 100
Potatoes 141 121
PROTEIN-RICH FOODS
Eggs 42 31
Cheese 55 45
Beef 21 51
Lentils 62 58
Fish 28 59
Baked beans 114 120
FRUIT
Apples 50 59
Oranges 39 60
Bananas 79 81
Grapes 74 82
SNACKS AND CONFECTIONARY
Peanuts 12 20
Popcorn 62 54
Potato chips 52 61
Ice cream 70 89
Yogurt 62 115
Mars bar 79 112
Jellybeans 118 160
BAKERY PRODUCTS
Doughnuts 63 74
Croissants 74 79
Cake 56 82
Crackers 118 87
Cookies 74 92

 

As you can see, most foods that are high GI foods also rank quite highly on the insulin index, but a couple of foods stand out for disproportionate insulin release: milk products, beef, fish.

But how is this possible? Well milk and most milk products contain a lot of sugar, so it makes sense why their insulin index would be higher and be contraindicated for insulin resistant individuals; but beef and fish? They contain zero carbohydrate, so what gives?

Even though carbohydrates are the major macronutrient from an insulin perspective, certain amino acids are capable of provoking an insulin surge as well. Take the branch chain amino acid leucine for example.

Leucine is particularly good at signaling “growth” of new muscle. Following a large protein meal when circulating leucine would be high, insulin is released to help pull amino acids from the blood into the muscle, stimulating new muscle growth.

By contrast, an insulin surge provoked by excess sugars will pull carbohydrates into the muscle. But when muscle glycogen levels are full, the excess sugar must be converted into body fat.

A day’s workout for the average Joe

Considering most of us aren’t terribly active on a daily basis, we have near maximal glycogen levels 24/7, as a result any excess sugar consumption tends to be quite detrimental.

Furthermore, unlike carbohydrates, purely protein foods not only result in increased insulin, but also cause your body to secrete glucagon. Glucanon is a hormone that opposes some of the potentially harmful effects of insulin. As a result, although high protein foods can cause a significant insulin release, they rarely have the same blood sugar crashing, hunger-inducing properties that high carbohydrate foods do.

Which means: better hunger control in the long run!

Therefore, despite the promise of classifying foods based on a single index, once again we are faced with an index that can at best be labelled “incomplete”.

Does this mean that all food indexes are destined for failure? Not necessarily.

In fact, the same researchers who developed the insulin index (Sue Holt and colleagues out of The University of Sydney), also did some work on a satiety index. Satiety, for those of you unfamiliar with the term, is a term used indicate how well a food satisfies a person’s hunger.

In my opinion, discovering what foods work best to nullify hunger is way more important in terms of real-world results than figuring out which foods cause the biggest boost in either blood sugar or insulin. But that’s just me and my somewhat bizarre belief that we need to value real world outcomes over results produced in a test tube or research lab… I know, I’m weird like that.

I’m only going to throw up a small version but you’ll get the idea. All the scores are based on a 240 kcal serving referenced back to white bread:

As you can see, even high glycemic foods like oatmeal and unprocessed potato do a great job of killing people’s hunger. Whereas certain foods promoted by dietitans everywhere as good weight loss foods (i.e. yogourt) do a pretty terrible job promoting satiety.

This is why I recommend oatmeal (and things like quinoa), potatoes and sweet potatoes be the starchy carbohydrates of choice for anyone serious about their health and body composition.

Not only do they contain less junk than breads, pastries and cereals, but they do a far better job helping control your hunger. Note, this still doesn’t give you carte blanche to eat oatmeal all day long, but opting for a filling, nutritious carbohydrate when your meal plan calls for carbs is just the smart choice in my books.

If I’ve said it once, I’ve said it 1000 times: if you control someone’s hunger, you’ll control their body weight over the lifespan.

So the next time someone comes to you preaching about the latest, greatest way to “judge” a food’s worthiness, ask them a simple question: “but will it help control my hunger?” If the answer is no, then odds are it’s not going to help you build a better physique over the long haul.

Till next time, train hard and eat clean!

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