I tried carb cycling for a month. The first 2 weeks sucked, but then my focus and performance dramatically improved.

Carb cycling, or alternating between high and low carb periods, is a growing trend among athletes who want the metabolic benefits of popular low-carb diets, without sacrificing energy or performance during heavy exercise. 

I'm a big fitness and nutrition nerd, so I decided to try the trend for myself to see if it would boost my workouts. 

While carb cycling did give me more focus and energy, it took a few weeks to adjust, with a lot of initial side effects like brain fog and fatigue.

I also had to cut out healthy foods I enjoy.

100 grams of carbohydrates may seem like a lot, but it adds up quickly. An apple — my favorite afternoon snack — weighs in at around 30 grams of carbs, almost a third of my daily carb budget. And foods like yogurt, almonds and protein shakes are surprising sources of carbs, too. 

Overall, I wanted more freedom to eat carbs for my intense exercise schedule — but I did learn how to be smarter about fueling my workouts. 

Carb cycling is about timing the majority of carbs you eat to coincide with exercise

The basic principle of carb cycling is to coordinate your carb consumption with exercise, so that the majority of carbs you eat are either before or after a workout. On less active days, you also eat fewer carbs. 

On high-carb days, I aimed to get about 50% of my daily calories from carbohydrates (about 250 grams of total carbs a day), 25% from protein, and 25% from fat. I'd have a small snack, like some fruit, after work and then exercise for one to two hours, immediately followed by a higher-carb protein shake. Dinner would be about an hour after working out. It often included carb sources like veggies, potatoes, beans, quinoa, or rice along with plenty of protein.  

In comparison, on low-carb days the goal was 20% of my daily calories from carbs (about 100 grams of total carbs a day), 30% from protein and 50% from fat.

On these days, I might have a low carb protein shake or plain, full-fat yogurt for breakfast, scrambled eggs with cheese for lunch, and some combination of protein (tofu, fish, or meat) and leafy greens for dinner.

I followed a pattern of two or three low-carb days in a row, followed by one high-carb day. I also matched my high-carb days to when I had planned more intense workouts. I usually do a combination of weight lifting, calisthenics, and running throughout the week, so I saved the carb-loading for days that I was lifting heavier or had a higher volume of strength training work.

I typically work out five to six days a week, so my workouts coincided with my low-carb days, too. 

Starting a carb cycling routine had side effects like brain fog and fatigue

It took about two weeks for me to adjust to a low-carb routine, during which I frequently felt groggy and low-energy. These side effects were most intense after two or more consecutive low-carb days, particularly if I was also working out. 

Waking up in the morning often felt difficult. While it usually takes me a little time and a cup of coffee to start my day, I found myself wanting to go back to bed for several hours after starting work.

As I worked, I often suffered from brain fog and struggled to concentrate. I wasn't specifically hungry or craving carbs, but I definitely felt less focused. 

I also had a persistent feeling of dry mouth and thirst, despite drinking plenty of water (and also electrolytes), which was unpleasant and distracting. At this point, I suspect my parched mouth was due to dehydration from lack of carbs. Water is the "hydrate" part of carbohydrate, and as your body runs out of stored carbs, it flushes water out, too.

The first few weeks of carb cycling made workouts more difficult 

Working out on low-carb days also felt like a chore for me, particularly cardio. 

In the middle of week two, I found myself exhausted after going for a light routine two-mile run. After my run, I felt light-headed and dazed. I had to rehydrate and have a snack before moving on to the second part of my workout.

These are common symptoms that the body is adapting to burn fat for fuel instead of carbs, sometimes known as the "keto flu." Most people experience them for a week or less — I may have taken longer to fully adjust since I was still including higher-carb days in my routine. 

After I adjusted to the routine, low-carb eating dramatically reduced my appetite and increased my focus

Starting around week three of carb cycling, I noticed some of the brain fog began to lift. I felt a bit more energized in the morning and felt much more able to concentrate on work and other activities. 

Most noticeably, I stopped feeling hungry during the day. I usually have a small breakfast around 10 am to hold me over until lunch at 1 or 2 pm. Suddenly, I wasn't thinking about food, and sometimes I wouldn't remember to eat anything until noon — and wasn't hungry after that for hours. 

This was inconvenient for me, since I wasn't intentionally trying to cut calories, and I wanted to make sure I was eating enough. It did help me understand, though, why people sometimes find low-carb or keto to be effective for weight loss. 

There's some research suggesting low carb diets reduce hunger by changing the levels of certain hormones related to appetite, which may have been happening for me. 

I also had more energy when I did eat carbs and better recovery after workouts

When I did eat carbs on this plan, I felt like their impact was more immediate and noticeable, giving me a boost of energy before workouts. This could have been a placebo effect, or because I was just excited to eat foods I enjoyed. And truth be told, I always look forward to exercising anyway.

What may have been happening to me internally, according to research, is that my pre- and post-workout carbs were keeping my muscles stocked up on glycogen, a carb-based form of energy needed to use and repair muscle during and after exercise. 

Another significant improvement was my post-workout recovery. I often exercise intensely enough to feel tired the next day, but not too sore. While carb cycling, I felt even less fatigue than usual — even after a hard workout. That allowed me to keep training hard, since I felt like my body was recovering well. 

I prefer a more moderate approach to carbs, but I'm more mindful now when I eat them

Ultimately, I went back to eating more carbs after a month because I was cutting out too many healthy foods I like.  I also work out too often to benefit from multiple low-carb days a week. It might make more sense for people who spend two to three days a week in the gym, or tend to have shorter, low-impact workouts. 

I want to adjust my diet to support my exercise routine, not the other way around, so I'm not sticking to a strict carb-cycling routine. However, I've definitely continued to time my carbs to coincide with my workouts, and I feel like the energy and recovery benefits have stuck around. 

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