why carbs matter

Why Carbs Matter Even If The Calories Are Low

February 17, 2021

When it comes to losing weight, we usually think that carbohydrates are the first thing that need to be removed from our diets to achieve results. It is important to know why carbs matter even with low calories in the food.

There are many fad diet plans out there that rely on carbs being eliminated from our diet in order to achieve the desired weight loss, such as Keto, Atkins, Carnivore, and more. If they allow people to lose weight, then why are they important to consume otherwise?

To Understand Why Carbs Matter, We Must Understand Them

There are two subcategories of carbohydrates: complex carbs and simple carbs.

Complex carbs are those that are high in fiber and have a lower glycemic index, aka they will not rapidly spike then plummet your blood sugar. These include non-starchy vegetables, whole grains, beans, lentils, milk products and fruit. Carbohydrates are the main source of fiber to promote gut health. It is important to consume enough fiber through complex carbohydrates to have regular movement throughout the GI tract.

Simple carbs are those that digest at a faster rate since they do not have a high fiber content. Examples of these are white bread, candy, sodas, table sugar, fruit juice and white rice. These are the types of carbs that usually have a bad reputation in the world of weight loss. This is because they are usually low in nutrients and do not provide a high satiety effect and they don’t keep you full for long. They also have a greater effect on blood sugar compared to complex carbs.

Importance of Eating Adequate Carbs on a Low-Calorie Diet

Maintain lean muscle tissue

  • Carbohydrates are “protein-sparing”, which means that they prevent the body from breaking down lean muscle tissue to supply energy to your body.2 During WLS, oftentimes there can be significant muscle breakdown in conjunction with rapid weight loss. It is extremely important to retain as much lean muscle tissue as possible as there are many important benefits of having a higher percentage of muscle mass which include increased calorie burn at rest, stronger bones, increased functional mobility, reduced risk of illness and injuries and more!

Energy and mood

  • Have you ever noticed that your mood tends to turn a bit sour when you’ve been dieting on lower carbs? That is because carbohydrates contain a non-essential amino acid called tryptophan that helps produce serotonin – the feel-good hormone – therefore, improving your mood.4 The important thing to keep in mind is to incorporate more complex carbs versus simple.


  • Carbohydrates are the primary source of fiber in our diets. Fiber promotes a healthy GI tract by bulking up the food we eat and moving it through our colon. Fiber also helps keep you full throughout the day since it takes a longer time to digest.3 Incorporating high fiber foods into your diet will help prevent grazing on low-nutrient snack foods between meals.

Prevents hypoglycemia

  • The primary and most readily accessible source of glucose is from carbohydrates. Glucose is what keeps your blood sugar levels stable throughout the day. An adequate intake of carbs prevents hypoglycemia, or low blood sugar. Feelings of low blood sugar include shaking, sweating, dizziness, lightheadedness, hunger, irritability, fast heart rate and headache.5 Incorporate a small to moderate portion of complex carbohydrates at each meal and snack to keep sugar levels from dropping.

Optimal brain and red blood cell function

  • Your brain is full of nerve cells (neurons) and it requires a lot of energy to function properly. Have you ever experienced brain fog or slight confusion when on a lower-carb intake? That is because your brain is not getting the adequate fuel it needs to work at it’s best! Although your brain can use fat and protein for energy, it takes more work to convert those macronutrients into fuel.6
  • Red blood cells also use glucose as their primary energy source. RBCs allow us to get adequate oxygen supplies to different areas of our body. If we don’t get enough oxygen, we can feel easily fatigued and winded.6

Vitamins and minerals

  • Carbohydrates have a variety of vitamins and minerals such as B12, thiamin, niacin, iron, potassium, phosphorus and magnesium. The more variety you include, the wider range of vitamins and minerals you can get!

So how should you incorporate carbohydrates into a balanced diet after weight loss surgery?

If you are approximately 6 months post op, the research states that approximately 90 grams per day is optimal. Also, since average calorie intake at the time is around 850 kcals/d, carbohydrate intake should be around 40-45% of total calories.1

If you are one year or further post op, around 120-130 grams per day is an optimal target. Average calorie intake at this time is approximately 1300 kcals/d, so a 40% carbohydrate intake would indicate the above goal.1

Keep in mind that carbs by themselves can pass through the stomach more quickly versus if they are paired with a protein or healthy fat.

Examples of Simple Meals and Snacks

(These are only examples, follow the recommendations of your surgeon and nutrition professional.)


  • 2 eggs scrambled + ¼ avocado mashed + 1 slice whole grain toast
  • ½ cup low sugar Greek yogurt + 1/2  cup frozen berries + ½ tbsp pumpkin seeds


  • 3 oz chicken + 2 tbsp hummus + 1 high fiber wrap + lettuce, tomato
  • 2 oz ground lean turkey + ¼ cup beans + ¼ cup reduced fat shredded cheese


  • 3 oz grilled salmon + ¼ cup quinoa + ¼ cup mango salsa
  • 3 oz tofu + ¼ cup pinto beans + side salad w/ low-fat balsamic vinaigrette


  • 1 reduced-fat mozzarella string cheese + ½ apple
  • 3-4 whole grain crackers + 1-2 tbsp nut butter
  • ½ cup low-fat cottage cheese + ¼ cup high fiber, low-sugar granola
  • 1 high-protein, low-sugar protein shake + ½ banana

The Take-Away of Why Carbs Matter Even If the Calories Are Low

Just like protein and fat, carbohydrates are essential in the proper functioning of our bodies. However, it is important for weight loss to be carb smart. Even with an overall goal of weight loss through low-calorie intake, carbohydrates are still a vital component of a balanced diet.


  1. https://bariatrictimes.com/recommended-levels-of-carbohydrate-after-bariatric-surgery/
  2. https://jamanetwork.com/journals/jama/article-abstract/440521
  3. https://www.hsph.harvard.edu/nutritionsource/carbohydrates/fiber/
  4. https://www.webmd.com/food-recipes/features/how-food-affects-your-moods#1
  5. https://www.uwhealth.org/healthfacts/nutrition/396.pdf
  6. https://www.eufic.org/en/whats-in-food/article/the-basics-carbohydrates
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jennifer davis


Jennifer Davis RDN, LD is a Registered and Licensed Dietitian Nutritionist. She works with bariatric patients on their diet and education for pre and post-surgery diet guidelines. She is always there for her patients at any point in their weight loss journey to answer questions regarding nutrition. She joined My Bariatric Solutions in December 2019. She has been in the health and wellness industry for 9 years and has over 10 years in customer service experience.