Macros Are Lying To You
If you ask someone deeply into fitness about what diet they’re following, the conversation will often devolve into a discussion of macros. For the uninitiated, “macros” is short for “macronutrients”: protein, fat, and carbohydrates. On a high level, you can decompose foods into these three building blocks.
Chances are you’ve heard about someone going keto: they’re eating few (near zero) carbs while getting most of their calories from fat and protein. Another famous macronutrient-focused protocol is the Atkins diet, which experienced a popularity boom in the mid-2000s and emphasizes protein over fats and carbs. Macros are a helpful tool that can reveal important information about a person’s nutrition. But by compressing a person’s diet into just 3 components, macros obscure the truth of what you’re eating and can lead you to be less healthy.
Before diving deeper into why that is, a brief digression.
For years, body-mass index (BMI) has been used as a way to quickly understand someone’s metabolic health in one number. The CDC says BMI is “[a screening tool] to estimate weight status in relation to potential disease risk.” The idea is that this number tells you something important about your overall health and risk of cardiovascular disease. BMI is defined as body mass divided by the square of the body height. If you have a BMI between 18.5–24.9, you’re healthy; if you’re 25–29.9, you’re overweight and if you’re above 30, you’re obese. This is all well and good until you examine what that means in practice.
Let’s take two people — let’s say two men, both 6’2”, both 225lbs — and they will have the same BMI: 28.9. So they’re overweight and quite close to being obese by the CDC definitions. But what if you know that one of them is Patrick Mahomes and the other is a totally sedentary office worker? Do you think they’re equally healthy, equally at risk for developing cardiovascular dysfunction?
Let’s unpack the chain of logic a little bit. What we ultimately care about is illness and premature death caused by cardiovascular disease: heart attacks, coronary heart disease, and strokes. A person’s relative body composition — how much fat vs. how much muscle they have — has been seen as a proxy for that risk; if you’re “fatter”, you’re perceived to be at higher risk. (Whether you actually are at higher risk is another matter entirely.) BMI is a proxy for that proxy: it’s not actually your body composition, but a stand-in for your body composition, which is in turn a stand-in for what we actually care about — directly-measured cardiovascular disease risk.
So if it’s such an indirect measure, why do we use it at all? People used BMI because it was easy. BMI originated in the 19th century from a mathematician — not a physician — who never intended for it to be used to measure individual health but rather intended it to be a government-level statistic to assess a population’s overall obesity level. Back then body fat was difficult to measure directly, and forget about any concept of biomarkers in an age before the widespread acceptance of the germ theory of disease. Even today it’s non-trivial to measure body fat accurately: some at-home smart scales claim the ability to do it via bioelectric impedance, but at best they give a rough estimate. If you want an accurate measurement you can use displacement — which involves submerging yourself underwater to be weighed after you’ve exhaled all the air from your lungs — or you can get a full-body scan like DEXA, which will cost you both time and money but is less physically uncomfortable than displacement. But even if you could measure body fat percentage instantaneously for free, that’s still not a direct indicator of cardiovascular disease risk.
What we should we use instead? We now have far more information about what data actually predicts cardiovascular disease and the cost of measurement has come down dramatically in the last 20 years. An annual lipid panel is both affordable and often covered by insurance, and is a much better place to start than body fat. It will give you important information like your total triglycerides, HDL, LDL, and VLDL circulating in your blood. If you want to go deeper, there are more specific markers like homocysteine, uric acid, and more that can help you and your doctor understand your unique nuanced risks. Also, this is where DEXA is more useful than a pure body fat measure obtained via another technique like displacement: DEXA can measure visceral fat — fat stored in your abdomen between your organs, as opposed to subcutaneous fat which occurs just beneath the skin — and visceral fat is directly linked to an increased risk of atherosclerotic diseases like heart attack, coronary heart disease, and stroke.
The upshot is that if you take all this information together — and combine it with your height, weight, age, gender, and genetic profile — it gives you a clearer picture about what’s actually going on inside your body and whether it’s something to be concerned about or not. The result is also more actionable: if you have it, you understand what specific risks are present and you can work with your healthcare practitioner to develop a targeted action plan to address them with diet, supplement, and lifestyle interventions.
So: BMI is bunk. But how does this relate to macros?
People care about macros because they’re a proxy measure of diet quality. They’re easily measured, just like BMI. And just like BMI, they’re misleading.
Generally speaking, eating too much sugar (a carb) is associated with pre-diabetes and diabetes, while eating too much saturated fat is correlated with higher blood pressure and increased risk of heart disease. So there’s a tendency to flatten these categories and view “too many carbs” as bad (which is very much in vogue at the moment), or “too much fat” as bad (which was quite popular in the 1990s). The result is a belief that if you just look at your diet’s macro splits — how much protein, fat, and carbs you’re eating — you can get a good sense of whether or not that diet is healthy. But this is just like saying that if you know someone’s BMI you have a sense of their long-term risk of cardiovascular disease. Without understanding the composition of the carbs, fats, and proteins in a diet — and a individual’s reactions to them — assessing the health of a diet on purely that basis can lead people to make decisions that actually increase their long-term health risks.
First, and most obviously: not all components of a macronutrient category are created equal.
Take carbs for example. Fiber, in macronutrient categorization, is a carb. If you have one 9g packet of fiber powder, from a macronutrient perspective you’ve consumed 9g of carbs. But the “carbs” you just consumed weren’t absorbed by your body at all. Rather, they either passed through you or fed the bacteria that live in your gut and produce hormones and neurotransmitters and otherwise keep you healthy and functioning. Fiber doesn’t provide energy your body can use and certainly won’t spike your blood sugar. In fact, diets higher in fiber generally improve blood-glucose response, reducing spikes and crashes. Macros don’t capture this. If you follow the blanket rule “carbs are bad” you cut out many good sources of fiber (fruits, whole grains, many vegetables), not to mention the other important nutrients those foods contain (antioxidants, flavonols, vitamins, minerals, etc.).
Carbs aren’t the only victim: proteins vary tremendously. Protein is made up of amino acids. Your body needs 20 different amino acids, each with different functions. For example, tryptophan helps make serotonin, an important neurotransmitter for mood, appetite, and sleep, while valine facilitates muscle growth, tissue regeneration, and energy production.
Your body can make 11 of the 20 amino acids it needs, but you need to get the other 9 through food. A “complete protein” food has all of those 9 . But not all proteins are complete proteins. Legumes lack methionine, while grains are short on lysine and sometimes threonine or tryptophan. But if you only looked at macros, you’d never know the difference. On top of that, the body has differing abilities to digest proteins in different foods. So just counting the grams of protein without regard to their source can lead to dangerous malnutrition.
(As an aside, this does not necessarily mean that being vegan is unhealthy. It just means that people following a purely plant-based diet need to properly diversify their nutrition to ensure they’re getting sufficient amounts of the 9 essential amino acids — all of which can be found in plant sources.)
Enough has been written about fats: saturated fats vs. unsaturated, omega-6 vs. omega-3, etc. More doesn’t need to be said here. Suffice it to say different fats have vastly different impacts on your health: some significantly increase your risk of heart disease while others reduce it. An avocado or a filet of wild-caught salmon is far better for you than factory-farmed grain-fed red meat, even though a serving of each may contain similar amounts of fat.
The upshot of all this is that viewing each macronutrient category as a monolith can lead you to make some tremendously bad nutritional decisions. You can design and eat a diet based around macro targets that consists of nothing but burgers, fries, and milk shakes — and even lose weight eating that exact diet — but that doesn’t mean you’ll be healthy. If all you look at is protein, fat, and carbs, an apple with almond butter looks the same as a cupcake. But the impact on your body of each of those two snacks, both short-term and long-term, is miles apart.
Second: people’s bodies react differently to different nutrients.
With the increasing availability of precision nutrition and diagnostic testing, we now have the ability to measure how different people’s bodies respond to specific foods.
For example, technologies like continuous blood glucose monitors (e.g. Dexcom, Levels) have come down in price dramatically in the last decade, enabling more people to directly see their blood glucose levels throughout the day. As a result, some may discover that foods generally regarded as healthy have uniquely adverse affects for their body. And blood glucose monitors are just one kind of test for seeing an individual’s response to food: there are other blood tests, not to mention saliva tests, urine tests, stool tests, breath tests, genetic tests — a whole panoply of diagnostic technologies that try to measure everything from hormone responses to circulating nutrient levels to gut microbiome composition to DNA methylation and much more beyond.
We’re only just beginning to understand and make use of all this new technology, so a word of caution is in order. While tests will continue to get cheaper and more accessible, not all have equal interpretability or clinical validity. There’s a lot of controversy, for example, about whether microbiome tests via stool samples tell you anything meaningful at all, or whether they just result in over-reaction to noisy samples:
One 2021 systematic review and meta analysis processed the data from 10 human gut microbiome studies and a total of 1,733 human stool samples. The authors of the review concluded that the web of human host-microbiota-metabolite relationships in the human gut is so complex that much more research is needed in order to decipher and characterize it. (Source)
The human body is an incredibly complex system. With the endless diversity of human diets and human bodies there’s a combinatoric explosion of possible causes for different effects. In time, and with the accumulation of more data on inputs and outcomes, we’ll develop a much clearer picture of what foods have what short- and long-term health impacts.
OK, that’s a lot of words. If macros are misleading, what should I do?
This may sound surprising, but I don’t want to completely discourage people from examining macros. The act of tracking them is useful because it helps people the same way that calorie counting does: the simple act of drawing attention to the nutritional content of what people eat actually nudges them to eat healthier. But it can’t stop there.
Macros are a gateway, an invitation to develop a more direct connection to the food you eat and how that food affects your body. Rather than collapsing all carbs (or proteins, or fats) into one monolithic group, it enables us to ask, what kind of carbohydrates am I about to consume? And if we all start paying a little more attention to what’s in what we eat, improved health will follow.
If we take a step back, the reason we spend so much time analyzing nutrition labels is because so much of our food is highly processed. Nutrition labels were an answer to the question: if our food system reduces food like corn, soy, wheat, fats, and proteins to their component parts and recombines them in highly engineered ways, how are we supposed to understand what we’re eating and what it might do to our bodies?
Nutrition labels are yet another proxy measurement, like BMI and macros. And they too lead us astray. The choice to include and feature certain pieces of information while excluding others is itself a statement of priorities. Even the use of a 2,000 calorie diet as “normal” for an adult is a barely-questioned assumption that, when scrutinized, doesn’t hold up. And as we learn more about the variations between individual bodies — not just age and gender but genetic makeup, hormonal balances, metabolic differences, environmental impacts and beyond — the idea that one standardized label could tell everyone with equal accuracy what they need and how a given food fits into their diet becomes increasingly risible.
In some far-flung future, everyone will empirically know what their body needs: what nutrients, when, and how much of them. But until that day arrives, what do we do?
Without falling prey to the naturalistic fallacy, a good rule of thumb is to try to base as much of your diet as possible on food that doesn’t have nutrition labels, especially fresh, organic produce. If you do this, you can better trust the signals your body is sending you about satiety. Processed food often tricks your body into feeling less full than the calories you’ve consumed. And many carbs consumed via whole foods — fruits and vegetables — come with fiber and water that both fill you up and moderate the impact of the sugars contained by those foods on blood glucose levels.
(As a quick clarification, “processing” is a general term that broadly refers to modifying raw food in any way. So both almond butter and Oreos are processed foods, but they vary in the degree of processing. Try to stick to minimally processed foods and foods where you understand the health impact of everything on the ingredients list.)
If you’re eating food that comes with a nutrition label, pay attention to it. Learn to identify the things that are more likely to be harmful. Avoid added sugars (and no, cane sugar is not meaningfully less bad for you than high fructose corn syrup) and steer clear of excessive saturated fat and sodium. (Salt, sugar, and fat are commonly used in processed food products both to extend the shelf life of the product and to make it taste good. If you stripped out the additives, many processed snacks would be disgusting.)
Don’t make purchasing decisions just based on how food products are named or marketed. Many “healthy” nutrition bars (cereal bars, protein bars, etc.) and snacks (e.g. trail mix — especially anything containing dried fruit) contain as much sugar as candy bars do. The health benefits claimed by these products are often marginal. Processed food products will often be produced using natural-sounding ingredients in the hope consumers will believe that makes the products better for them. Case in point: fruit juice concentrate, which is nutritionally nearly identical to sugar or high fructose corn syrup, but allows manufacturers to say something like “Contains real fruit!” Don’t fall for this. (And avoid fruit juices in general unless you have a specific health need.)
Our society’s relationship with food is changing. 200 years ago, we were concerned with just having enough food to survive. 100 years ago we generally had enough food but wanted to make it all tasty and convenient: more calories with more flavor for more people for less money. Now we’re increasingly aware of the cost of those highly-engineered foods on our bodies, so focus is turning to how the food system we’ve created keeps us alive but also makes us sick: diabetes, heart disease, hypertension, inflammation, immune system dysfunction, gut dysbiosis, hormonal imbalances, and more.
We have an opportunity to rethink what and how we eat. Every day we vote on the food system we want in the world with our buying decisions. Not everyone has the patience to learn about nutrition in detail, the money to buy organic or grass-fed or pasture-raised (etc.), or the time to make meals from scratch. It’s still a luxury. But that can and will change if we want it to.
People eat what makes them feel good. Previously that could be interpreted very literally: food that tastes good. But it increasingly means food that makes you feel good about what you’re eating: food that reinforces your identity as a healthy person who is taking care of their body so it can serve them long into the future. And we’re also only just beginning to understand how what we eat today impacts future generations: there is increasing evidence that diet affects gene expression and transmission.
We’re learning so much, so quickly about how deeply our nutrition affects our bodies, their microbiomes, and the trajectory of the whole human race. It’s such an exciting time to be alive. The more awareness we bring every day to what we eat — the more conscious we are of how our food choices affect us, how they are us — the longer, healthier, and richer our lives will be. Choose wisely, and be well.
