How Many Carbs Should I Eat?

how many carbs should I eat?

Several months ago, I overheard Person A talking to Person B about what he did to lose weight. 

Person B: “So how’d you lose all that weight?”

Person A: “I cut my carbs down to next to nothing,” he said. “Now I’m down 40 pounds!”

Person B: “Hm, I might have to try that!”

I froze. I knew Person A was spewing potentially damaging information to Person B. A carb-restricted diet might work for Person A, but it might not for Person B. Person A also failed to mention to Person B that he cut his calories.

Losing weight is about more than carbohydrate consumption. It’s about how many calories go in and how many calories go out. 

This conversation was the tipping point to me to see out something I’d been thinking about for months, a nutrition certification. I’m fed up with seeing nutrition nonsense in my Facebook feed and hearing it from others. I want to do what I can to set the record straight about carbs, calories, and nutrition overall. 

I want to learn science-based nutrition guidelines to use in my life and to help others on their journey to a healthier self. 

It turns out that the American Council on Exercise had put their specialization courses on sale right as the pandemic shook things up, so I figured I could finally tackle my ACE Fitness Nutrition Specialization with my extra time. 

Becoming a Fitness Nutrition Specialist will help you develop expertise in all areas of nutrition education and promotion that are within the scope of practice for health and fitness professionals.

As part of my studying, I’ll be writing articles about the hypothetical case studies that are included in one of the texts for the certification, Sports Nutrition for Health Professionals (2nd. Ed.). This accomplishes at least three goals for me: it helps me practice what I’m learning, it gives me great blog content, and I’m hoping it leads me to connect with people who need help with their fitness nutrition. 

The book does not include the correct answers, so I’ll develop my answers based on what I’m reading in this text and link out to relevant, legitimate (i.e., not some jabroni you’ve never heard of) sources when appropriate. Please use these articles as reference points, but they may not be appropriate for your specific situation. 

Case 1: Kate, The Cross-Country Runner

Kate is a cross-country runner who wants to make sure she is consuming sufficient carbohydrates for optimal athletic performance and to spare protein. She needs about 2,700 calories per day. Answer the following questions regarding Kate’s recommended carbohydrate intake.

Carbohydrate Needs

1. Based on the AMDR for carbohydrates, how many grams of carbohydrates should Kate consume per day (provide a range)? 

You might be asking yourself first, “What’s AMDR?”

AMDR stands for Acceptable Macronutrient Distribution Ranges. It’s the range of a particular macronutrient—protein, fat, or in this case, carbs—that is “associated with reduced risk for chronic diseases while still providing adequate intake of nutrients such as vitamins and minerals.” (source: Institute of Medicine). 

AMDRs are expressed as percentages.

The AMDR for carbs is 45-65 percent.

If Kate is eating 2,700 calories a day to fuel her runs, then Kate should consume between 1,215 calories (45%) and 1,755 calories (65%) of carbohydrates per day. 

This would equal 303-438 grams of carbs. A single gram of carbohydrate = 4 calories, so 1,215/4 = 303 and 1,755/4 = 438. 

2. Provide four high glycemic load sources of carbohydrate that she could consume when she needs a quick energy boost.

To understand glycemic load, we must first look at glycemic index. 

Glycemic index ranks carbs based on their blood glucose response. High-GI foods enter the bloodstream rapidly, spiking glucose levels. On the other hand, low-GI foods are digested more slowly, causing a more gradual increase in blood glucose levels and a small boost in insulin levels. 

Glycemic load accounts for portion size. It is the glycemic index of a food multiplied by grams of carbohydrate divided by 100 (GL= GI x grams/100).

When Kate needs a quick energy boost, she could pick from these foods that have a high glycemic index:

  • Carrots (92 GI)
  • Corn flakes (80 GI)
  • White rice (72 GI)
  • White bread (69 GI)

3. Provide at least eight foods that she could consume throughout her day that are low glycemic index carbohydrate sources.

Kate could eat these foods throughout the day:

  • Low fat yogurt (14)
  • Lentils (29)
  • Skim milk (46)
  • Apples (39)
  • Oranges (40)
  • Whole wheat pasta (42)
  • Sweet potatoes (48)
  • Oatmeal (49)

I should note that later in this text (pg. 138), the authors mention that “despite years of research on glycemic and endurance performance, there is still no agreement about how glycemic index affects performance.” 

Case 2: Adele, The Active Octogenarian

Adele is an 85-year-old woman who recently moved to a retirement community after her husband died. With the move, she also decided that she would make significant lifestyle changes, starting with eating “healthier” and exercising more. One of Adele’s daughters just started a low-carbohydrate diet and convinced Adele to start with her. Now Adele wonders if that was the right decision to make. 

Carbohydrate Needs

1. Adele is on a very low-carbohydrate diet (about 15% of calories from carbohydrates). She eats about 1,600 calories per day. What is the difference between the amount of carbohydrates that Adele is advised to consume and how much she gets on this diet? 

At 15% of calories from carbohydrates, Adele eats only about 240 calories (1,600*0.15 = 240) or 60 grams (240/4) of carbohydrates a day . 

The AMDR suggests eating 45-65% of calories from carbohydrates, which would equal 720 calories (180 grams) to 1,040 calories (260 grams) from carbs. 

2. What are the possible complications for Adele’s exercise program resulting from her new diet? 

If Adele loses weight, her carbohydrate restriction may play a part in that. But she would be losing water weight. “Glycogen requires water for storage,” according to the Sports Nutrition for Health Professionals textbook. “When these glycogen stores are broken down in response to carbohydrate deprivation, the body excretes water.” 

Carbohydrates and Exercise

Adele frequently participates in water aerobics classes. Lately she says that she has had decreased energy and it is increasingly difficult to get through the class.

1. What might be some nutritional reasons why Adele has low energy?

Carbohydrate is the body’s preferred source of energy. Without carbs, Adele may feel sluggish, fatigued, or exhausted. 

2. How would you tell Adele to modify her diet?

I would encourage Adele to follow the AMDR for carbohydrate ranges for a few weeks to see how she feels during her workouts. 

Special Considerations: Low Glycemic Index Diet 

Concerned about Adele’s waning energy levels and her overall health, her physician requests that she abandon a very low carbohydrate diet. He says she should try to consume a low glycemic load diet. Adele asks you what this means.

1. Explain how you would describe a low glycemic load diet to a layperson. 

One way to lower glycemic load and reduce your blood sugar spikes is to eat whole, minimally or unprocessed foods. Foods high in glycemic load include 

Harvard Medical School lists several foods you can switch to lower your glycemic index, such as whole fruit instead of fruit juice, quinoa instead of white rice, and whole wheat bread instead of white bread. 

Train Yourself: Carbohydrate Needs

Based on your weight, what carbohydrate range do you need in a day? (Use the recommended carbohydrate intake formula for athletes by The Academy of Nutrition and Dietetics on page 10.) 

My weight averages out at 173-178 this year, so let’s assume a nice round 175 for my weight.

The carbohydrate intake formula for athletes that is referenced is 2.7-4.5 g/lb of body weight per day. 

  • 2.7g * 175 = 472.5 grams (1,890 calories) of carbohydrate
  • 4.5g * 175 = 787.5 grams (3,150 calories) of carbohydrate

I can tell I’m not an athlete at this level because I eat around 2,500 total calories a day. 

Think back to all of the food you ate in the past 24 hours. Complete a dietary recall of your intake. Approximately how many grams of carbohydrates did you eat? How did this compare with your recommended needs? How much fiber did you consume? Did you reach the recommended 14 grams per 1000 calories? If not, what foods could you incorporate into your diet to help you increase your fiber intake? 

I have been tracking on MyFitnessPal for probably two years, at least. 

I ate 211 grams of carbs yesterday (as of this writing). I had used nutrition service, which gave me 215 carbs on this particular day. The numbers I’m learning in this book are much different than what I’ve learned through the service I used. My allotted carbs—215 grams, or 860 calories—was 39% of my total caloric intake (down from the recommended minimum of 45%). 

As of this writing I’m officially heading out of a cut so my carbs (and calories) are on the rise. 

My fiber was only 18 grams, so I was a little low there. I could have eaten more fiber by eating more vegetables or more fibrous fruit.

Photo by Anastasiia Chepinska on Unsplash