Is the High-Carb, Low-Fat Diet Right For You?

by Ace Ryder


Since the pandemic hit and we’ve mostly stayed at home, it’s not surprising that many of us have gained a pound or two. Apart from exercise, there are tons of diets available on the internet and one of which is the high-carb, low-fat diet.

Nutritionists and doctors agree that the acceptable macronutrient distribution is 45-65% energy coming from carbohydrates, 10-35% from protein, and 20-35% from fats. This goes against the common misconception that carbs are bad for the body, and demonstrates that carbohydrate is the essential macromolecule we need in our daily food intake.

Some think that eating bread, pasta, or rice is a major no-no if you are planning to lose weight. Carbohydrate is a food group that has been often vilified by fad dieters and influencers. But should you cut it out? The answer to that is a resounding: Not really. It is the excess calories that pack on the weight and give you love handles; not the carbs, per se. A high-carb, low-fat diet is not the only diet that can lead to weight loss.

The truth is, at the end of the day, a calorie deficit is the main factor for weight loss.

Calorie deficits can be achieved not only by eating less, but also by burning calories through physical activity and exercise. As long as your heart rate increases, you can burn calories.


Aerobic Metabolism vs. Anaerobic Metabolism

Is the High-Carb, Low-Fat Diet Right For You?There are two main types of metabolism that our body undergoes to produce energy.

One is called aerobic metabolism wherein the body can create around 36 up to 106 ATP per cycle (Note that ATP is the primary fuel for muscles at the molecular level) depending on whether it uses glucose or fats as substrate. This process takes more time to finish compared to anaerobic metabolism. Aerobic metabolism is often used by the body for low to moderate intensity activities requiring sustained energy production such as swimming, brisk walking, cycling, and running. “Cardio” exercises usually fall under this category.

The second one is anaerobic metabolism, which the body uses when oxygen is not readily available in our bloodstream. Unlike aerobic metabolism, which yields tons of ATP, this process only produces around 2 ATP per 1 molecule of glucose.

However, each cycle can end at a much faster rate. It also exclusively uses glucose as its primary source of ATP. Exercises that require short bursts of energy in a short amount of time, such as weightlifting or HIIT, employ anaerobic metabolism as their primary energy source.


Why Choose High-Carbs, Low-Fat Diet?

Who could benefit from a high-carbohydrate, low-fat diet? Here are some potential reasons why individuals might wish to go on such a diet.


The Role of Carbohydrates in Anaerobic Exercises 

Let’s take a look at how the following anaerobic exercises are affected by carbohydrates.

  • Strength Training Programs. When doing strength training such as weight lifting, if you eat low amounts of carbohydrates, your glycogen stores will not be replenished and will become depleted over time. And as we know, glycogen is a polysaccharide, which functions as the glucose reserve in the body. And when you exercise, your body needs to take up glucose to provide energy to your contracting muscles. Within your first few lifts, you might be feeling good, but after a few minutes, you’ll exhaust your glucose reserves. That means no more power to get through the rest of your routine. Be reminded that glucose breaks down into ATP, which enables your muscles to work.
  • High-Intensity Programs. Another well-known workout is high-intensity interval training or HIIT. Compared to strength training, HIIT relies more heavily on anaerobic metabolism to harness and release bursts of energy within a short amount of time. Once you go beyond 90% of your maximum heart rate, your body switches to anaerobic metabolism; high-intensity workouts help you attain that level. Consequently, your body will rely more on your glycogen stores. If you are eating lower amounts of carbohydrates than usual, you may not meet the energy demands of your muscles, leading to fatigue.


The Role of Carbohydrates on Aerobic Exercises

Since aerobic exercises give the body an option to either use glucose (from glycogen) or fats to generate energy, they will be less affected by changes in your carbohydrate intake (eg. choosing high-carb over low-carb, or vice versa).

This was proven through the research of Phinney (1983), wherein he documented the effect of a zero-carb diet (also known as the keto diet) on the athletic performance of 5 healthy cyclist volunteers at 62-64% VO2 max (the range where fat metabolism is preferred over glucose for aerobic respiration). They found that there was no drastic change in terms of the average performance of the five subjects.

However, given the small sample size of this study, and the wide intervals among the performance of each volunteer, this result should still be taken with a grain of salt. In addition, despite not negatively impacting the volunteer’s performance in low to moderate intensity activities, it still reduced their performance for sprinting. Moreover, once an individual goes beyond 70% VO2 max, there is strong scientific evidence that low-carb can decrease performance for aerobic activities.

Also, many world-class marathon runners engage in “carbo-loading” when training for competitions. They eat anywhere from 441-607 grams of carbs daily leading up to the big day to maximize their glycogen stores, improve endurance, and delay muscle fatigue. This goes to show that there could be a role for carbohydrates even in aerobic exercises.


Choosing What’s Best for You

Is the High-Carb, Low-Fat Diet Right For You?Doing your research before committing to a particular diet is always recommended. You should consider what your goals are, whether you want to do aerobic or anaerobic exercises, what your lifestyle is, and if it would be beneficial to your overall health in the long term. Carbohydrates should not be viewed as bad for the body if taken in the appropriate amount. It is, in fact, a major source of our energy.

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