macros microscope

Your Macros Under a Microscope 

Consuming carbohydrates, fats, and protein gives your body the components it needs to rebuild, recover, and thrive. But not all macros are created equal. 

(Unit 5 of 7)

You know macronutrients — the nutrients your body needs for maintenance and energy. Balancing protein, fat, and carbohydrates, which serve as your body’s basic building blocks for both fitness and just plain survival, is the name of the game for any diet worth its salt.


Carbohydrates from grains, breads, legumes, sugars, fruits, and some vegetables break down primarily into glucose, a vital energy source that operates in all tissues (even if you’re on a zero-carb diet, as your body can make glucose from other sources).


Protein from meat, fish, poultry, dairy, eggs, nuts, beans, lentils, seeds, and even a lab (think engineered “meat” substitutes) provides the essential amino acids your body needs to repair and build muscle, tissue, and organs, among other things.


Fats store energy, cushion your organs, and aid vital processes involving hormones, absorption of fat-soluble vitamins, and cell membrane integrity. The pie chart of your macro consumption is called your “macronutrient split.” Adjusting your split can help you better match your exercise and health needs, and your unique “tolerability” or “responsiveness.”

The Science of Macros

Simple, right? But here’s the thing: scientists studying nutrition and microbiology have surpassed these entry-level assumptions about the “simple” nature of macros. In fact, recent science reveals a number of misconceptions about how our bodies interact with protein, carbs, and fats. Here are some tenets the CrossFit athlete needs to know about the evolving science of macros.

How much protein can you absorb?

How Much Protein Can Your Muscles (and the Rest of Your Body) Absorb?

Much myth has been made around how much protein your body can absorb from a meal. Often, the focus has been on just how many grams of protein your body is actually garnering from that double lean beef burger (wrapped in lettuce, of course—”beef in a leaf” style) you crushed after your WOD. Sounds simple: how much protein is going to waste from such a meal, and what’s the perfect protein intake after a workout — a.k.a. your body’s “maximal anabolic response”?

Amino Acid Concentration

But a systematic and direct measurement of how much protein your body can absorb is surprisingly complex. One recent marker identified by scientists is the concentration of amino acids — which comprise proteins — appearing in the blood after a meal.


Another is insulin, the release of which is triggered by select protein-comprising amino acids—the higher the protein dose, the higher the blood insulin response. One recent study of the anabolic response to protein (that’s the difference between protein synthesis and protein breakdown within the body) used these markers to show that, in both young and old test subjects (in a non-exercising state), eating 70 grams of protein (considered a high intake level) triggered a higher rate of muscle protein and whole-body protein synthesis and a lower rate of protein breakdown than eating 35 grams of protein (a moderate intake level). In short: your body can absorb a lot of protein, so go to town.

As we’ve noted, though, it’s not entirely that simple. It’s critical to distinguish between the anabolic response, which relates to protein synthesis throughout the whole body, and muscle protein synthesis, which relates specifically to protein made for skeletal muscle. Another recent review showed that more than half of the whole-body anabolic response after a workout involves non-skeletal muscle tissues like the gut, organs, and bone or connective tissue. Takeaway: eating a lot of protein helps your skeletal muscle tissue get stronger — and even more so, helps the rest of your body with important repair and other processes. Whether this translates into greater gains — in performance and muscle mass — awaits convincing evidence.

Fats & The Microbiome

Love Your Fats. Your Microbiome Does.

Fats, or lipids, are very large — and very important — molecules. Without them, your body wouldn’t be able to store energy reserves; your organs would be unprotected from the physical trauma of a fall while attempting a triple-under; important hormones couldn’t be produced; and your cells wouldn’t be able to build their membranes. You should eat a lot of mono- and poly-unsaturated fats, including extra virgin olive oil, nuts and nut butters, fatty fish, and avocados. Saturated fat is saturated in hydrogen molecules and is mostly found in fattier meat sources like beef, pork, lamb, poultry with skin, and dairy products like butter and lard; eating it in large amounts can increase your blood LDL cholesterol, a highly controversial outcome that may (again) relate to gut microbiome and permeability elements rather than ‘sat fats,’ per se. Trans fats — found in margarine, doughs, and fried foods — are, as you know, a no-no.

Another benefit of the “good” fats? Eating plants that are rich in them appears to support our microbiome, the vast ecosystem of bacteria, viruses, fungi, and archaea living inside your gut and other parts of your body. A recent review asserted that plant-based diets rich in mono- and polyunsaturated fats increased the diversity of the gut microbiota — which may be desirable, considering that a lack of gut microbiota diversity is associated with diseases like Crohn’s, IBS, and colorectal cancer.

The Gylcemic Index

Carbohydrates: Debunking Glycemic Index Errors — and a Focus on Fiber

Your body breaks carbohydrates down into glucose, an important and immediate fuel for your body. The glycemic index (which has been misunderstood and misused for decades), compares the blood glucose response between a food that delivers 50 grams of digestible carbs and a standard carb, often glucose itself or white bread (in an amount delivering 50 grams of carbs). Importantly, the glycemic index (GI) of a food is thought to directly reflect the rate of digestion and entry of glucose into the systemic circulation. White bread, for instance, which includes many simple carbs that quickly and easily are converted into glucose by your body, has a “high” glycemic index: eating it causes the glucose in your blood to spike, and quickly. An apple, on the other hand, would appear to cause a lower, “slower” release of glucose in the blood — giving it a “low” glycemic index.

But might this be too simple an approach to a complex carbohydrate breakdown process? A fundamental assumption regarding low-GI foods is that they produce a low glycemic response as a result of a slower rate of digestion of carbohydrate in the intestinal lumen, and that this subsequently slows the absorption of glucose into the circulation. But a study from 2003 examined glucose removal from the blood by tissue as an important albeit unappreciated ‘other half’ of the glycemic index. Scientists at the University of Texas Austin noted that corn flakes (“high” GI) and bran cereal (“low” GI), despite having very different blood sugar “spikes,” delivered their glucose to the blood at nearly identical rates. Translation: corn flakes were no faster than All-Bran® cereal. Why? The glucose that entered the blood from the All-Bran was removed (think of it being “drained” out) much faster in the first 30 minutes after eating (due to a much higher insulin response—think of insulin as a “drain opener” into muscle, in healthy persons). This increased glucose removal response by tissues caused the bran cereal to have “low” GI response, despite its glucose entering the blood at effectively the same rate as that from the corn flakes. In short: low doesn’t always mean slow, and high doesn’t always mean fast.

Fiber & The Microbiome

One final note on carbohydrates: Some carbs contain “food” for your gut microbiome — dietary fiber. Specifically, your microbiome “eats” by fermenting otherwise non-digestible fiber, from foods including garlic, onions, leeks, asparagus, bananas, seaweed, and more. This fermentation process releases short-chain fatty acids (SCFAs) that provide important anti-inflammatory processes in your body. So, if you remember one thing about your macros, remember this: select your carbohydrates wisely, and your microbiome will show its appreciation.

Also Check Out…

The Microbiome and Your WOD (Unit 1)

What’s Going On Inside Your Gut? (Unit 2)

Recovery from Your WOD—with Microbes in Mind (Unit 3)

Diet and Your Gut Microbiome: A Primer (Unit 4)


About the Author:

Anthony L. Almada, MSc, FISSN is a member of the research and development team at Seed, which develops probiotics to impact human and planetary health. He is trained as a nutritional and exercise biochemist (UC Berkeley). He has been a co-investigator on over 50 university-based clinical trials exploring the effects of diet, dietary supplements, and therapeutic interventions upon muscle performance, body composition, whole body metabolism, and joint function in health and disease. In 1990 he created the “thermogenic” category. In 1993 he co- founded the first company to introduce creatine monohydrate to North America. He has worked with CF Games and Regional athletes, top Olympic gold medal swimmers, professional cyclists, physique athletes, and NFL teams. He has been part of Seed’s R&D division since late 2018.

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October 24, 2023 10:00 am


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