Glycemic index. We hear about this all of the time, right? And it is essential information to understand, it gets to the root of the "carb" conversation, which is so loaded and so confusing for so many people. But it is NOT the end all be all and there are some big misconceptions on how to use the glycemic index to guide food choices. So let's chat first about WHAT the glycemic index is and then about how you can utilize this in making decisions about what to eat or not eat for long term health (and weight loss).
In the 1980s, a Dr. Jenkins in Toronto found that carbohydrates raised glucose levels when eaten, but fat and protein did not. Additionally, he found that different carbs raised our glucose levels by different amounts. While a carbohydrate is an essential part of our diets, this showed not all are equal.
A SIDE RANT: CARBS
I'll get into this in another writing (don't worry, carbs is too loaded to not discuss in detail) but by simplifying "carbs" into "bad or good", we are doing ourselves a disservice (just like we talked about language and simplification with fat). A quick explanation for now.
"Carbohydrate" means glucose (a type of sugar) molecules linked together with "linkers". These carbohydrates can be simple (short chains, easy to break the links and release glucose, usually created in lab) or complex (weaving bands and combs and swirls of linked glucoses, harder to break down, usually sourced naturally), obviously we want to stick with more the complex carbohydrates.... not all carbs are "bad".
Going along with this, glucose in itself ALSO is not "bad". In fact glucose is essential and your body uses it directly to input it into your energy production cycles to keep you and your metabolic and physiologic processes going and you ALIVE. The problem comes when you have constant input of glucose or quick spikes of glucose or the inability to use it or store it appropriately. So not to overly simplify (just like I said not to LOL), in general avoid simple carbohydrates and eat whole food, whole grain complex carbohydrates and don't eat all of the time.
Anyway, back to the glycemic index.
Each carbohydrate molecule will load you with glucose to some degree. Dr Jenkins tried to come up with a way to determine objectively how much load of glucose each carb molecule gave you, and, then objectively, when combined together as a food, what the index of the load was for the food as a whole. Glucose was given the highest value of 100 by Dr. Jenkins in the 80s, and all other foods are measured against that on the glycemic index scale. So, the Glycemic Index (GI) is a relative ranking of carbohydrates in types of foods according to how they affect blood glucose levels (basically combine all of what is in each food, see what the area under the curve does and call it an index).
Carbohydrate laden foods with a low GI value raise your blood glucose less highly and cause a lower and slower rise in blood glucose and therefore, usually, lower and slower rise of insulin levels (insulin is in charge of storing extra glucose in adipose and liver and muscle when you've used what you need for your energy production). When we are talking about "low carb foods", we are essentially talking about those that contain carbs with a lower glycemic load, and, hence, the entire food has a lower glycemic index. So, this is why we are eating low to no sugar, low to no grain/flour, and the veggies grown above ground that are less starchy.
Refining a carb, such as purifying or concentrating it, will increase the glycemic index. Removal of fat, fiber and protein in this refining process also means that carbs can be digested and absorbed quickly, and the GI goes up. Wheat that is refined into highly processed wheat foods (pasta, flour, bread) has a high GI versus choosing something that is stone milled that will not pulverize it as much and thus will have a lower GI. Or in juice, you can take all the carb fiber out and drink the amount of fructose in 5 oranges easily; whereas, it would be hard to take in 5 oranges just to eat. Does that make sense?
Generally, aiming for combined GI for the DAY of 45 is best because we know from numerous, observational cohort studies around the world that the daily average GI of the diet of people in the lowest quintile (20% of the population) is about 40-50. Similarly, in a meta-analysis in diabetes care of 15 experimental studies investigating the role of low GI diets in managing diabetes, the daily average GI was 45. This average GI has been proven to have significant health benefits in people with existing diabetes and in reducing the risk of chronic diseases like heart disease and diabetes.... And people can, and do, achieve it in real life.
So it seems simple. Stay with low GI foods and you are good? Unfortunately, it isn't that simple.... some examples
- White bread has a GI of 73. Coca cola soda is 63. Now white bread is obviously not good for you, but worse that Coke???
- Fruits have a very low GI, even though they have fructose in them, because of the metabolism of it's sugar (fructose) is entirely different than that of glucose. And eating many fruits can be very good for you, unless you are juicing them or processing them, then they have an entire different metabolic injury on us that isn't captured by the Glycemic Index. .
- Peanuts are about 7, because they are mostly fat and protein, so they don't have glucose to load you with. Does this mean they are fine and you can eat them all day and all night? What about the calories?
The glycemic index isn't the whole story because it doesn't take into account WHEN you are eating these low GI foods and doesn't get into what happens when those foods are combined with different types of fat and protein or fiber, and it gets confusing based on serving size. So, it really is just one tool of many. A few other tools that might help more..... Glucose load and Insulin index.
A GLUCOSE LOAD Is a more much more useful tool, in my opinion, because it takes on the value of the WHOLE meal (not just the individual food) a bit more clearly. Additionally, this is where it becomes more clear that VEGGIES are not a carb laden problem (you hear that Keto-ers?). To get the glucose load, you take the percentage of carbs in the entire meal (grams of carbs / 100) x the glycemic index of the total MEAL to get the glycemic load of the meal. This is more helpful when choosing foods than just straight GI.
To be honest, though, you know me at Wholist, I'm not a counter. I don't suggest counting calories, I don't suggest counting macros, I don't suggest calculating your GI/ GL. You will drive yourself insane. It is not sustainable for the long term and that is what we are talking about here, long term weight maintenance and health. We talk about it though, because I am all about education, evidence and empowerment. If you can understand the WHY about all of this and have someone to help you consistently choose better (our coaches), you will soon automatically be making the right path forward.
And MORE. Weight reduction isn't successful with just low GI diets because it isn't just glucose that causes weight gain.... it is insulin and cortisol that do (as well as the balance of leptin and grehlin and more). The goal should be to balance ALL of these with sleep, exercise, vacations from eating, mindfulness, stress reduction, mindset work for interpretation of choices, and the right types of real food. Too much to get into here (come check out our coaching programs for personal attention and daily podcasts on weight science and mindset work), but for now let's talk about how to measure insulin.
As I alluded to above, insulin is a hormone that reacts to foods and help store excess glucose in adipose, liver, muscle for later use as energy when you need it. It communicates in a host of other ways with other hormones that are essential for inflammation, cognition, mood, weight, metabolism and more. Simplification is that insulin is the key hormone to weight issues and a key hormone in metabolic syndromes and inflammatory diseases.
The insulin index is something that isn't talked about nearly as much as either of the glycemic scales, but in my opinion could be more important. I am going to pretty much just quote Dr. Jason Fung of Obesity Code fame about this because he is so right on. All food causes insulin secretion. When we talk about protein and fat and fructose, they will also inch your insulin even though they don't raise glucose (so can't be measured on a glycemic index which makes it useless in this case). Insulin can and IS raised independently of blood glucose (sugar) and this is essential information for us to understand. With carbohydrates, there is a pretty clear dose response of insulin to the glucose ingestion, but together carbs are only responsible for 23% of the variability of the insulin response. The vast amount, 77%, of the insulin response has nothing to do with blood glucose. The rise in insulin can also be ranked and measured, it just isn't as well known or utilized. A few reasons why we should be concentrating on the insulin index instead....
- The glycemic index measures the rise in blood glucose in response to a standard portion of food, and the insulin index measures a rise in blood insulin in response to a standard portion of food. And this is quite different than the glycemic index. Not surprisingly, we see that insulin surges with high carb foods. But, what was surprising, is that dietary proteins can also cause a similar surge. The glycemic index doesn't consider fats and proteins at all because they don't raise glucose.
- The glycemic LOAD counts for percentage of carbs in the meal, so it is a little better, but it doesn't account still for the proteins and fats. And, so, that in effect ignores the fattening effects of two of the three macronutrients we eat.
"Insulin drives weight gain, and that changes everything. This is where the low GI diets fail. You can lower the glucose response but you aren't necessarily decreasing the insulin response." Dr Jason Fung
Pay attention to the glycemic indices and loads, but realize that it isn't the whole story (nothing is). Pay attention to the whole meal and consider how to utilize the ideas of the glycemic index, glycemic load and insulin index into your choices without driving yourself crazy..
Real food. Complex whole grain and whole veggie foods. Sleep, mindfulness, exercise, stress reduction are essential. Don't eat all of the time, give yourself insulin vacations.
And as always, we are here for you if you want a focused coaching program to learn all of this (and tons more), heal food relationships and lose/ maintain weight! Additionally a FREE SNACKING FREEDOM CHALLENGE is available here, 7 days of podcasts and documents and advice, a great jump start to better health and weight maintenance.
Dr Heather Hammerstedt is a board certified lifestyle medicine physician and board certified emergency medicine physician. Find her at love.wholisthealth.com to find out more about services she offers, including 12 week transformative coaching programs on food/weight and fitness, lifestyle telemedicine consultations, speaking engagements, podcast interviews and more. @wholisthealth on all social media platforms