Starting in 2018, the Guelph Victors launched a Running Speaker Series. First up, on Jan. 23, was “The Carb Controversy”, a detailed presentation about nutrition by Victors runner (and dietician) Cara Kasdorf. Here’s a summary. (Download her full presentation here.)
#1 The Carb Controversy
It turns out that “Carb Controversy” isn’t much of a controversy after all for dietician (and runner) Cara Kasdorf, who spoke to a crowd of nearly 40 runners at the first Runner Speaker Series event sponsored by the Guelph Victors, in January 2018.
In recent years, Kasdorf has worked with numerous athletes and members of the general public who have tried a low-carbohydrate, high-fat (LCHF) diet in order to lose weight or improve performance. (This is also called a “keto” or “ketogenic” diet, and it attempts to adapt the body to burning fats instead of carbs as its main energy source.)
According to Kasdorf, there is “little research to support the long-term benefits” of an LCHF diet. She did acknowledge that the diet might be tempting for athletes who want to lose weight, and that it might be useful for ultra-endurance runners (those who do day-long or multi-day events). For those who are determined to try the unproven diet, Kasdorf recommends they do it with the supervision of a dietary expert.
Here’s what the low-carb diet involves: while a moderately active runner would normally consume 300–420 grams of carbohydrate per day (this example assumes a 130-pound runner who exercises an average of 5–7 hours per week), the LCHF diet restricts carbs to 20–50 grams per day. (That’s about the equivalent of a single banana, a cup of pasta, or half a bagel.) The transition to this reduced level of carbs takes 1–3 weeks.
Ultimately, Kasdorf says that the latest science she’s reviewed (at the Canadian Nutrition Society conference in mid-January) suggests that fat adaptation in athletes “may actually be caused by the down-regulation of their carbohydrate metabolism” — resulting in decreased performance. In other words, the long-term fueling off of fat can impair the body’s ability to process glycogen.
As a result, Kasdorf says she doesn’t recommend the diet “for most athletes.” (The references for Kasdorf’s assessment are at the end of her full presentation, link above. She examines low carb training on slides 28–32.)
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In fact, most of Kasdorf’s talk was spent on the positive benefits of carbohydrates as a fuel source for runners, and especially how to fine-tune their consumption around training and racing.
One of the lesser-known benefits of carbohydrates (besides fueling) is their role in keeping us mentally alert and positive as we run. When carbs get depleted (as can happen during a long run or race) our “perception of effort” goes way up, even before we hit the wall and actually run out glycogen (the quick burning form of carbohdrate that is stored in our liver and muscles).
But carbs aren’t the whole story of a healthy diet, says Kasdorf. She says runners need to balance carbs with protein, fats, along with some attention to fibre (which is a form of carbohydrate), as well as vitamins and minerals.
She displayed a sample menu that would provide about 300 grams of carbohydrates (enough for a 130-pound, moderately active runner), along with proteins and fats (see below). Kasdorf advocates sprinkling these three main nutrients in small portions throughout the day, with special attention to snacks (note that her AM and PM snacks contain all three nutrient groups).
Kasdorf also discussed what to eat before training or in longer races (over 90 minutes duration). She recounted one of her early marathons, when she and another dietician attempted to carbo-load by eating double their normal carbohydrate amounts in the two days prior to their race (a strategy she recommends). But they made the mistake of taking too much of the food in the form of complex carbs (whole grains), and so they arrived at the start line feeling bloated and with too much fibre in their systems!
Everyone makes mistakes. So her caution was this: plan your pre-race nutrition carefully, and choose carbs that are low in fibre (sports drinks, some fruit, white breads, rice or pasta).
For races lasting longer than 90 minutes (half-marathon, marathons and further), Kasdorf has a single piece of advice for your nutrition on race-day: “Don’t wing it!”
By this she means, calculate an exact plan to consume 30–60 grams of carbohydrates every hour after the first hour (roughly, ½ an energy gel plus ½ cup of sports drink every half hour). Since our bodies only store about 1700 calories of glycogen in our muscles and liver, and since most people will burn 2,500–3,500 calories in a marathon, it’s essential to take on fuel during the 42 kilometre event if you want to avoid hitting the wall (depleting all your glycogen).
In a shorter race like a 10K, it can even be beneficial to have a swig of sports drink and then spit it out, especially in the second half. Why? Because the small amount of sugar can trick the brain in its perception of hard effort, easing the psychological struggle of the closing kilometres.
Kasdorf closed her talk with a list of the ways that dieticians can help runners:
- develop a general nutrition plan to support training
- create a carbo-loading plan for the week prior to a big race
- detail a race-day nutrition and hydration plan
- address any dietary deficiencies (like low iron, or other minerals)
- review the use of non-dietary supplements
For more information, you can contact Cara Kasdorf here, or ask your family doctor to recommend a consultation with a dietician, especially one with a sports nutrition background!