The Role of Carbs in an Active Lifestyle

Clients always ask me about carbs. How much to eat, should you avoid, do carbs make you fat, etc. This is a VERY broad and far-reaching topic, as it encompasses many other “hot topics” (e.g. gluten/wheat, Ketogenic diet, dairy, added sugars/refined carbs, FODMAP diet, and so on). So let’s focus today on carbs within the context of exercise.

To start, I will summarize some basic but key points to consider:

1. Carbohydrate is a macronutrient found naturally in healthy plant-based foods like fruit, starchy veggies (peas, corn, potatoes, winter squash), beans/legumes, and whole grains, as well as in dairy. Non-starchy veg have carbs too, but in low amounts.

2. Carbs are also found in less nutrient dense foods like white pasta/rice/bread, chips etc as well as in candy, baked goods, soda, etc. (this is where “added sugar” and “refined carbs” come into play).

3. All carbs break down into simple sugars, including glucose (i.e. energy), which is the preferred fuel source for working muscles.

4. Any glucose that isn’t used right away is stored in the muscle and liver, and broken down later when needed (e.g. during sleep and exercise).

5. These stores are limited, unlike our fat stores, so you have to eat enough carbs daily to fuel exercise (among other things) and preserve your lean body mass, especially on more intense and/or longer (>60-90min) training days. If you eat more carbs than you store and burn, they are converted to fat (i.e. why carbs can be “fattening”). If you consume extremely few carbs, your body is forced to tap into fat stores for energy (leading to dietary ketosis), but this isn’t appropriate, nor sustainable, for many people.

6. We can burn both fat and carbs for fuel, but we burn a greater proportion of carb as intensity increases due to less oxygen being available. During lower intensity exercise, the body is able to rely more on fat as a fuel source and prolong glycogen stores as a result. Aerobic exercise helps us become more efficient at burning fat as fuel, but still, without carbs you will likely struggle to perform well at higher intensities.

Okay, so what does all this mean? First, carbohydrates are not evil. They are a necessary part of the diet, especially for anyone engaging in moderate/high intensity and/or endurance exercise, and should not be “cut out” entirely. Does that mean you must eat dairy/wheat/whatever else? No – if you feel better or find greater success with weight loss by eliminating certain foods, that’s fine, as long as you are eating enough calories from a wide variety of other healthy foods to support your activity level and get the nutrients your body requires. Just ask yourself whether or not this way of eating is sustainable for you.

I usually have my clients focus on choosing healthier sources of carbs (see point

1) and portion controlling / balancing them with protein and fat for slower digestion / greater feelings of fullness. Pre-exercise is when we skew more towards carbs (e.g. something easy to digest like a banana right before a ride), and sometimes we opt for lower fiber carbs (reg pasta/rice etc can be helpful here), but this is based on individual tolerance/preference. On the whole, we usually lower total carb intake for weight loss, while being mindful of eating enough to exercise well (i.e. fluctuating intake so that it matches training days). Lastly, note that carbs themselves do not make you gain weight; overeating in general and following an imbalanced diet that is skewed more towards carbs (especially refined ones) likely will, though!

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