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Your fitness questions answered (Courtesy of Cycling News)

Food intake, nutrition planning

Hi All,

Could you please advise best food intake regime prior and post exercise, I’m about to hopefully start shedding approximately 50kgs through both cycling and boxing.

I’m currently working nightshift from midnight until around 8:30am and I plan to train after work then go to sleep.

At present my diet needs changes in both content and quantity but I also need a few pointers with regards to when is ideal for eating and what I should eat at certain times

Appreciate any help you can provide

Thanks

Mark

Pamela Hinton says:

Hi Mark,

Although each athlete’s training diet should be individualized to meet their particular needs, a few general principles apply. Obviously, if you want to lose body fat, you must expend more energy than you consume. You can accomplish this both by increasing your training volume and/or intensity and by reducing your energy intake. However, you do not want to short change your body on the fuels needed for training or on the nutrients needed for recovery and training adaptation.

If you are regularly (i.e., multiple times per week) training for more than 90 minutes at a time at moderate-to-high intensity, you need to be sure to be sure that you are eating enough carbohydrate. Here’s the reason that dietary carbohydrate is essential for endurance athletes who train for prolonged periods of time. Our bodies prefer to use carbohydrates and fats (not protein) for energy during exercise. At rest or during low-intensity exercise (<50% of VO2max), the preferred fuel is fat. This fat can come from our diets if we’ve just eaten or from our fat stores if we’re between meals. As exercise intensity increases, our bodies have to shift from fat to carbohydrate to generate energy.

At maximal exertion, we use only carbohydrate. In situations where oxygen demand is high (i.e., high-intensity exercise), carbohydrates have an advantage over fats because less oxygen is required to produce a given amount of energy. Dietary carbohydrate is important because the carbohydrate stored in our bodies as glycogen in the liver (240 kcal) and muscle (1400 kcal) is in limited supply. When our glycogen is gone (usually after 1.5-2 hours of exercise), we literally run out of fuel and have to markedly decrease our exercise intensity (i.e., switch back to using fat).

There are two strategies to prevent depletion of glycogen during
exercise: start with “full” glycogen stores and consume carbohydrate during exercise. To maintain glycogen stores, endurance athletes should consume 6-10 g of carbohydrate per kg of body weight (target body weight) in their usual diet. The pre-training meal should provide 100-300 g of carbohydrates, depending on workout duration and intensity. During a training ride of >90 minutes, the recommended intake is 30-60 grams of carbohydrate per hour. Drinking 16-32 ounces of a commercial fluid-replacement beverage that contains 4-8% carbohydrates every hour would meet this guideline. Most energy gels contain about 25 g of carbohydrate, and these work fine as long as they are taken with water to avoid gastrointestinal distress.

Post-exercise nutrition is focused on recovery, which includes both repletion of glycogen stores and synthesis of skeletal muscle protein.

The optimal way to replete glycogen stores is to consume 1.5 g carbohydrate per kg of body weight (target body weight) within 30 minutes after exercise and again every 2 hours for the next 4-6 hours.

Carbohydrates that are easily digested and absorbed, i.e., high glycemic index, will allow for rapid repletion of muscle and liver glycogen. Exercise increases the rate of protein breakdown and synthesis in skeletal muscle and, with adequate nutrition, it can have an anabolic effect on skeletal muscle. Carbohydrate consumed post-exercise is beneficial because it reduces the rate of protein degradation.

However, to increase protein synthesis and achieve a net increase in muscle mass, it is important to consume protein after exercise. Studies have shown that consuming about 0.2 g of protein per kg of body weight per hour during the first 2-3 hours post exercise results in net protein synthesis.

While these guidelines are by no means comprehensive, they should provide some guidance on pre- and post-training nutrition.

Good luck!

Pam

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