“The simple answer as to why we get fat is that carbohydrates make us so; protein and fat do not” Gary Taubes, Why We Get Fat
“When you eat mostly high-nutrient foods, the body ages slower and is armed to prevent and reverse many common illnesses. The natural self-healing and self-repairing ability that is hibernating in your body wakes up and takes over, and diseases disappear. A nutrient-rich menu of green vegetables, berries, beans, mushrooms, onions, seeds, and other natural foods is the key to achieving optimal weight and health.”
―Joel Fuhrman, The End of Diabetes: The Eat to Live Plan to Prevent and Reverse Diabetes
The war over ideal macronutrient content of the diet seems to be never-ending. Library shelves (or more relevantly, blog archives) are filled with widely varying titles: low-carb destroys your body in this way… low-fat that destroys your body in that way… How to lose weight on a high carb diet… How high carb diets cause obesity…
At the same time that the vegan/vegetarian movement is showing a large increase in numbers, we see the low-carb/ketogenic diet sweeping the world, both touted as the best way to lose weight and reverse disease.
This war over the proper macronutrient composition for the human body seems to continuously rage on, and to what avail? A frustrated and confused population who just wants to know what food to put on their plate.
When we get confused we look to the experts in the field, and what do we see? Journalists like Gary Taubes sending the message that it is the carbohydrate that makes us fat, while fat and protein are innocent. Meanwhile doctors like Joel Fuhrman send the message that to cure disease, we have to eat a plant-rich diet, loaded with carbohydrates. (Note: this is no critique on either of these men – they both provide wonderful rationale for their ways of eating, despite sending very different messages).
I write this article today to help sort out the confusion – to sift through arguments for and against carbohydrates and fats. Note that debate over pros and cons of different macronutrients is not a bad thing – it is absolutely important to sort out the details on how each macronutrient contributes to health or disease. However, this war over which macronutrients are good and which ones are bad, or which diet (low-carb vs low-fat) is best, is absolutely absurd, because both carbohydrates and fats play crucial roles in healthy functioning, and because both diets are great at supporting a healthy diet, when done correctly.
I am here to tell you that there is no need for a war over which argument is correct because both arguments make excellent points which can be translated to healthy dietary decisions. Both a low-carb and a low-fat diet can be great ways to lose weight and improve health markers, along with ones that ignore macronutrient ratios altogether.
The question then, is which method should you use to achieve your health goals (high-carb or low-carb), or even better, do you need to worry about macronutrients at all?
I am going to focus primarily on carbs and fat because these are the two at the heart of all the debate. Don’t mistake this to mean protein is innocent or less important; rather, levels of protein intake are extremely important, and intakes above or below what is adequate for your body can be very detrimental to your health. But when we talk about trade-offs for macronutrients, we should really only be talking about eating more or less fat or carbs. Protein levels should always be at a moderate intake level, regardless of your diet (with some individual variability, based on genes and physical activity).
For our discussion today I will focus on two key markers of health: weight and insulin sensitivity. I choose these markers to help make my case on macronutrients because these factors are linked to almost every single chronic disease we face today.
Things I will not discuss today are the direct effect of macronutrients on cardiovascular disease, which you can read about here, or the outdated model that claims we should eat low fat because we should control our calories, which you can read about here.
Let’s get started.
When we make decisions on which foods to consume, we need to think about the signals the foods will send to our own body. This is in contrast to the idea that we should focus solely on the calorie dose received. Calories become far less important when you consider how a high caloric meal containing lots of fat and protein will put the body in energy burning mode, while a low-calorie, refined carbohydrate meal will send the body into a viscous insulin cycle, leading to energy storage, and likely lead to more eating soon after.
The signals sent from the foods we eat are what is most important. The caloric content is secondary, and thus the daily total caloric load is mainly a byproduct of those initial signals (again, see my previous article on the subject if this idea is off-putting).
While I go through some of the signals that different foods send to the body, keep in mind the large amount of variability between individuals. Based on the chemical makeup of our bodies (e.g. genomes and epigenomes, along with the health of our cells), the response to these signals will vary, but the overall mechanisms still hold true.
We all know those people that can put any food, in any quantity, in their bodies and not gain a pound, while others eat one slice of cake and their body goes haywire. Reasons for this range in ability are plenty, including variations between individuals’ genome and epigenome. At the end of the day what it really boils down to is how one’s hormones respond to the signals it receives. When it comes to weight, it mostly boils down to the insulin response of the individual. Those with genes that result in a higher insulin response will be more prone to storing energy (1).
For example, eating high glycemic foods, whether it’s a potato or doughnut, tells the body to store energy. On the other hand, foods like green, leafy vegetables, along with fats like coconut oil, keep the body out of fat storage mode and allow the body to burn energy. We have to keep in mind that the extent to which these foods cause a fat storage signal is dependent on the state of the body of the individual consuming these foods. If that individual is (epi)genetically programmed to be hyper-sensitive to glucose, or has unhealthy cells due to years of abuse with industrial foods, then that person will have a stronger fat-storage response to a food such as a potato.
If you find yourself frustrated with your genetic luck, do keep in mind that weight isn’t everything. Just because one body is better at putting on extra weight does not mean that that body is unhealthier. Actually, in some cases, bodies that are better at storing fat can end up healthier. As we will learn, extra energy floating around the body, in the form of glucose or fat, is dangerous for the functioning of cells throughout the body. Bodies that are better able to tuck that fat away safely in fat cells can reduce their risk of damage by all that freely-roaming energy, although it may result in an increase in fat mass. Additionally, some bodies are better at producing more fat cells to tuck energy away, and these individuals tend to have lower levels of inflammation and insulin resistance (2).
To improve our overall health – whether it is to lose weight, avoid/reverse insulin resistance and diabetes, or prevent heart disease, there are a few key ideas to discuss, and they all have one central focus: insulin and insulin resistance. Note that the different health problems we wish to avoid that I stated above (weight gain, diabetes, and heart disease) – these may sound like very different diseases – but in reality, they all have one thing in common: again, insulin and insulin resistance.
Body Weight and Insulin
Body weight is a direct result of your body’s ability to handle the energy it takes in with the energy it expends. Yes, I do mean “the body’s ability.” Body weight is not a simply a result of your ability to manage your energy; rather, it is almost entirely up to the hormones inside the body and the signals they receive. These hormones can either signal the need to store energy or burn energy. What these hormones do is based on the food you put in your mouth.
To go any further, I have to make sure we all understand the main energy storage hormone: insulin. I have an entire article devoted to this very important hormone, so if you are entirely unfamiliar with it I suggest you head over there. For today, just remember this: simply put, if levels of insulin are high, the body stores energy. If levels of insulin are low, the body can release energy and burn fat. Insulin is released primarily in response to glucose, but glucose content of a food is NOT the only factor resulting in an insulin response (much more on this soon).
Remember:
High Insulin = energy storage AND no fat burning
Low Insulin = energy release AND fat burning
Let me explain what I mean as “high” and “low” levels of insulin, as I don’t intend these to be as clear-cut as they sound. Having low insulin levels does not mean that we never want to raise insulin. Rather, what we want to avoid is chronically high levels of insulin. These high levels can occur for different reasons. One reason is insulin resistance, in which cells stop responding to insulin, causing the body to produce more of it, leading to chronically high levels of insulin. I will discuss this problem in depth in my next article in this series.
The other way to achieve high levels of insulin is to regularly consume foods that spike insulin. If your goal is to burn fat, but you eat insulin-stimulating foods throughout the day, then the body is not going to be able to burn fat; rather, it is going to be stuck in a state where energy is constantly stored, and very little can be released. This will be the main topic for the rest of this article – getting the body away from fat storage mode (high insulin) to low insulin conditions, where the body is able to burn fat.
Finally, when I say high and low, what may be more accurate is to say whether the insulin response is “normal” or “not normal.” There is more to an insulin response than simply the maximum insulin release. For example, the time it takes for that insulin to go back down to baseline, along with with the shape of the curve returning to baseline, can have a large impact on metabolism. A normal insulin response consists of a modest increase in insulin, followed by a steady decrease back to baseline. However, some foods, like highly refined carbohydrate, can cause a large spike in insulin, resulting in a crash of those insulin levels. This leads to a corresponding drop in glucose levels, often times resulting in hypoglycemia, or low blood sugar levels, which will cause us to reach for anything sugary to get glucose levels back up.
Figure 1: Simple graph of possible insulin responses. Normal and low insulin responses, shown in blue and green, respectively, are preferred to the “insulin spike” shown in red.
For the purposes of this article, when I talk about foods with low insulin responses, this means that, overall, less insulin is released in response to that food, and therefore less energy is stored. For this, think about the green curve compared to the blue curve: overall the insulin dose is lower and less energy is stored. Additionally, keep in mind that second component, that a high insulin response often causes an irregular insulin-response curve, which leads to further metabolic damage. For this, think about the red curve compared to the blue or green curves. When insulin is spiked, you get a surge of insulin, followed by a steep decline, resulting in the well-known sugar crash that leaves you reaching towards the closest candy bar.
Now back to the function of insulin:
At the cellular level, high levels of insulin signal to cells to take energy inside for storage. This could either be in the form of glycogen, the short term stored form of glucose, or triglycerides (fat), the long-term storage version of any macronutrient. During low insulin levels, cells are able to release this stored energy to be burned for fuel.
Body weight is a function of insulin. Chronically high levels of insulin mean constant fat storage. Only during low levels of insulin can the body burn its internal energy (i.e. burning of fat stores). That means that if you are focused on losing weight (burning fat stores for energy), but keep your body in a state of high insulin, then you are not going to be able to make progress, and will only end up frustrated, and likely in a poor state of health.
It is important to note that insulin and fat storage is not a bad thing. This beautifully designed system allows for the storage of energy during times of eating, followed by the release of energy when the body does not have access to food (e.g. while sleeping, or during times of famine).
Moreover, energy storage does not have to be in the form of fat. Glycogen is the short-term storage of glucose. It gets stored in places, such as muscle, to be used as a quick, efficient source of energy when your muscles need to work hard. When these sources of glycogen get depleted, it is important to eat some carbohydrate, which stimulates insulin, to resupply these depleted glycogen stored.
The problem is that now this system has been tilted in one direction, towards chronic energy storage. This, in combination with the excess amount of energy we consume, causes longterm storage of fat, along with an inability to release that fat for burning (3).
Since body weight is a function of insulin levels, the important thing for us to know is what controls insulin, which brings us back to our discussion of macronutrients.
Controlling Insulin Levels
The war over macronutrient ratios is strongly linked to how macronutrients vary in their ability to raise insulin levels. While the main ideas of this argument are strong, there is great confusion when it comes to understanding which foods raise insulin the most.
Each macronutrient has a different effect on insulin. The simplified version divides macronutrients by their ability to stimulate insulin: fat does not induce an insulin response, protein induces a moderate insulin response, and carbohydrate induces the largest insulin response. While this trend is generally true, the problem is that it gets more complicated than that. It turns out that breaking the different macronutrients into a null, moderate, and a large response is overly simplified and may lead to poor dietary choices.
Another common system used to understand insulin response is the glycemic index (GI), which measures the amount of glucose released in response to digesting a particular food. Because the amount of glucose in the blood is largely what dictates insulin levels, low GI foods have a low insulin response, and high GI carbs have a high insulin response. This classification does not fully capture a food’s effect on its insulin response, but it does a good job showing which carbohydrates tend to increase insulin more than others. For example, high GI carbs like potatoes will increase insulin levels more than a low GI carb like broccoli. However, a low GI food like meat (animal muscle), can induce a large insulin response, even though it is a low-carb food.
This shows us that insulin levels are a function of more than just glucose/macronutrient composition. In addition to glucose content, various natural compounds found in high levels is whole plant foods, such as fiber and polyphenols, can mitigate the insulin response, (4,5) and therefore whole foods with all the nutrients still intact will tend to elicit lower insulin responses (4,5).
Let’s take one study to show how this works: In a 2013 randomized, controlled, crossover study (4), healthy women ate a variety of high-glycemic meals and were tested for glucose and insulin responses. The effect of two different breads (white bread vs. rye bread) was studied along with the addition of berries to that bread. Common belief may lead us to think that the bread would cause a large insulin response, and adding more sugary berries would increase that response.
What they actually found was that the highly-processed white bread caused a larger release of insulin compared to the rye bread, but even more interestingly, the addition of berries to either bread reduced the insulin response. They determined that this reduction in insulin was caused by the high fiber content of the berries, along with their low acidity, both of which have been shown to lower the postprandial (post-meal) insulin response. What this shows is that our simplified view of sugary, carb-based foods increasing the insulin response is not necessarily true. Rather, the addition of foods containing micronutrients can actually reduce the insulin response, even if it does involve adding more glucose to the system.
Overall, I think it suffices to know this: Insulin response to carbohydrates depends on the processing level of that food, including factors such as the fiber content of the carb, along with its antioxidant content (4-6). Fiber decreases the rate of digestion, lowering the amount of glucose released. Meanwhile, compounds like polyphenols reduce the overall insulin response (4,5). Therefore, generally speaking, the closer a food is to its whole, natural form, with all the micronutrients intact, the lower the insulin response. The more processed that food becomes, the larger the insulin response, because important compounds (e.g. fiber and polyphenols) lower the insulin response (4,5).
The other thing about insulin is that grouping foods can either amplify or mitigate the response. For example, if you eat a bowl of pasta, then you will get a fair insulin response. Add some lean chicken breast to that pasta and the insulin response will go up! But add some vegetables, loaded with antioxidants and with a high fiber content, and the insulin response goes down, because adding fiber and polyphenol – rich foods decrease insulin responses.
Or you could skip the pasta and eat a bowl full of whole plant foods, and have a very small, normal insulin response, which will (most likely) not result in any fat storage. Or eat an avocado, or a spoonful of coconut oil, both consisting purely of fat, and have no insulin response at all, leaving your body in a fat burning state.
I hope this discussion of insulin helped you see that while, yes, macronutrient composition does affect the insulin response, the big picture is not really so simple. Eating carbohydrates will cause an insulin response, which in turn leads to fat storage; but, the type of carbohydrate (low vs. high glycemic; whole vs. processed) has a major influence on the details of the insulin response. Additionally, other foods, including fats and proteins, can also stimulate insulin, depending on the individual, and the form in which they are consumed (7).
Remember, this is important because keeping insulin levels low is key to allowing the body to burn fat, while chronically high levels of insulin result in fat storage.
So far this discussion has been on insulin in a healthy body – bodies that have the proper, natural response to insulin. We call these individuals insulin sensitive, because their bodies respond properly to the insulin signal, and therefore levels fluctuate normally in response to foods.
However, around half of our population today has lost this insulin sensitivity. This means that around half of us today do not respond properly to the insulin signal, and therefore have lost the ability to respond properly to the energy contained in foods. The results are disastrous, and likely at the root of our chronic disease epidemic (12).
Therefore it is crucial to take measures to fix this problem. To do that, we first must focus on consuming foods that elicit normal, low insulin responses. Second, we must work to fix this loss of insulin sensitivity, which I will discuss in the follow-up article.
And now, the important question: What do I put on my plate to avoid insulin secretion and fat storage?
Now that we understand insulin and its control over metabolism, we can start to think about what foods that we, as individuals, should eat.
To lose weight, we have to keep insulin levels low, so that energy in the body gets burned, not stored. How best to do this depends on the individual, but what it generally comes down to is how your body responds to the energy you consume.
The battle over macronutrient intake becomes irrelevant when you understand that the important thing is keeping insulin levels low. Yes, high-fat diets are the easy way to do this, because fat generally does not stimulate insulin. If you eat a diet of mostly fat, with reasonable amounts of carbohydrate and protein, then it is easy to keep insulin levels down, so that fat never gets stored, and the energy consumed gets burned (8,9). And no, high-fat diets are not dangerous diets that will make you die of a heart attack (8). The effectiveness of a high-fat diet for all markers of health, including metabolic markers and cardiac markers, have been well documented (8, 9).
However, the same improvements can be achieved with a low-fat diet, although it might be a little bit more difficult. It is possible to lose weight and improve metabolic factors while consuming a low-fat, high carbohydrate diet (e.g. vegan), but when consuming carbohydrate it is easier to eat foods that may lead to some fat storage, such as starchy foods like bread or potatoes. If you consume a whole food plant based diet, one high in whole food carbohydrates and moderate in fat and protein, then insulin levels tend to stay low, due to the high micronutrient density of the food (4,5). Additionally, it becomes difficult to consume enough calories to gain any weight when eating only plants, which naturally will lead to weight loss.
However, I do have to caution you on this last point. Yes, a low-fat, high (whole, good quality) carbohydrate diet can result in weight loss, due to the low-insulin response from whole foods, along with the overall low caloric content of the diet (plants are low in calories, so it is difficult to overeat!). However, this strength (low calories) can also be this type of diet’s greatest weakness. Many people who try a low-fat diet often don’t last long, due to the low-caloric, low-satiating quality of diet. Contrary to common belief, when trying to lose weight (and keep it off), it is important to get enough energy to support healthy functioning, and often, eating a diet entirely of plants makes this difficult. Therefore, it can be beneficial to supplement a whole foods, plant-based diets with foods that are more calorically dense and more satiating.
But then again, a whole foods, vegan diet may be the perfect way for you to lose weight.
When it comes to choosing a diet style that will help you achieve good health, what it comes down to is this: how does your own body respond to the foods you eat. If you currently have a metabolically healthy body with naturally low insulin levels, then chances are the macronutrient composition doesn’t so much matter. However, if you have certain predispositions to foods, or otherwise have damaged the metabolic health of your body, then one diet (low fat vs. low carb) may very well be more beneficial for you.
For example, certain genes put you at risk for adverse reactions to specific foods. One well-known gene, the FTO gene, results in dangerous responses to high levels of fat, particularly saturated fat (10). If you have this gene, then avoiding high levels of saturated fat is imperative, and therefore a diet lower in fat and higher in carbohydrate may be beneficial.
On the other hand, if you have a naturally high insulin response to carbohydrates, then a low-carb, high-fat diet could be the best choice for you to lose weight and improve metabolic health (1, 11).
All things considered, at the end of the day, the diet you can stick with is the diet that works best. Although I firmly believe that our tastes for different foods are highly adaptable, such that almost anyone can grow to like most foods, some people are going to strongly resist one diet over another.
If the idea of eating loads of fat revolts you, then you likely aren’t going to be able to stick to a high-fat diet, and one that focuses more on plant foods might be better for you. On the other hand, if life without bacon and butter makes you want to cry, then shifting to a diet based on plant foods and very limited in fats is not going to work.
And of course, in most situations, it might be best to ignore the idea of macronutrients and eat what makes you happy, so long as your food sources come from real, whole foods, and your body responds with a normal insulin response.
Disclaimer: As always, I am not a doctor, nor am I a certified nutritionist/dietician. This article should only be used as information to help you make your own decisions. If you have any serious health problems, always consult a licensed health professional before making any drastic changes to your diet.
References
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2. Moreno-Indias, I., & Tinahones, F. J. (2015). Impaired adipose tissue expandability and lipogenic capacities as ones of the main causes of metabolic disorders. Journal of Diabetes Research, 2015. http://doi.org/10.1155/2015/970375
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9. Feinman, R. D., Pogozelski, W. K., Astrup, A., Bernstein, R. K., Fine, E. J., Westman, E. C., … Worm, N. (2015). Dietary carbohydrate restriction as the first approach in diabetes management: Critical review and evidence base. Nutrition, 31(1), 1–13. http://doi.org/10.1016/j.nut.2014.06.011
10. Phillips, C. M., Kesse-guyot, E., Mcmanus, R., Hercberg, S., Lairon, D., Planells, R., & Roche, H. M. (2012). High Dietary Saturated Fat Intake Accentuates Obesity Risk Associated with the Fat Mass and Obesity – Associated Gene in Adults 1 – 3. Journal of Nutrition, 142(5), 824–831. http://doi.org/10.3945/jn.111.153460.risk
11. Pittas, A. G., Das, S. K., Hajduk, C. L., Golden, J., Saltzman, E., Stark, P. C., … Roberts, S. B. (2005). A low-glycemic load diet facilitates greater weight loss in overweight adults with high insulin secretion but not in overweight adults with low insulin secretion in the CALERIE trial. Diabetes Care, 28(12), 2939–2941. http://doi.org/10.2337/diacare.28.12.2939
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