Nutrition for Sport and Exercise

A Practical Guide

Hayley Daries

• Publisher: Wiley-Blackwell
• Year: 2012
• Print ISBN: 9781405153546
• eBook ISBN: 9781118359747
• Edition: 1
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

Food and drink choices before, during and after training and competition have a direct impact on health, body mass and composition, nutrient availability and recovery time, and an optimal diet can significantly improve exercise performance. Nutrition for Sport and Exercise outlines the fundamental principles of nutrition in relation to sport and exercise and then applies these principles through practical tools such as food and nutrient lists, recipes and menu options. This practical guide translates the athlete's goals into achievable strategies and shortens the gap between theory and practice. Equipping the reader to successfully implement dietary changes, this is an invaluable resource for athletes, sports physicians and undergraduate students of nutrition and sport and exercise science courses.

Special Features

• Dedicated chapters on the impact and relevance of specific nutrients and food groups
• Includes recipes and menu options
• Covers the area of sport and exercise nutrition with an evidence-based approach
• Concise and accessible, combining theory and practice

CHAPTER 1

Introduction

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Key Terms

Energy balance

Positive energy balance

Negative energy balance

Nutrition knowledge

Dietary goals

Food group models

Dietary reference values (DRV)

Guideline daily amount (GDA)

Dietary extremism

Practical food skills

Travel fatigue

Body composition

Estimated average requirement (EAR)

Performance analysis techniques

Physical demands of exercise

Preceding diet

Training adaptations

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The importance of an adequate diet for athletes

It has been clearly demonstrated that the nutritional composition and adequacy of an athlete’s diet has an impact on performance and overall well-being. The consumption of food and fluid as fuel and hydration, before, during and after training and competition, can affect the athlete’s nutritional and immune status, health, body mass and composition, energy stores and nutrient availability, exercise performance and recovery.

Participation in all types of exercise, ranging from recreational exercise to competitive sport increases the physical demands on the body. Their increased energy expenditure requires athletes to consume higher energy intakes and specific amounts of nutrients from food and fluids, in the pursuit of meeting the demands of sport and exercise. Therefore, an important goal of an adequate diet for athletes is achieving and maintaining energy balance, which aims to restore energy reserves and leads to greater fulfilment of health and performance goals. While positive energy balance (when energy intake is higher than energy expenditure) encourages weight gain, negative energy balance (when energy intake is lower than energy expenditure) can result in weight loss. However, there are consequences to both positive and negative energy balance that need to be considered in the long term. Positive energy balance may lead to over-fatness and chronic illness, and negative energy balance may result in an increased risk of muscle tissue loss, fatigue, injury and illness.

An adequate diet involves more than just energy balance, as key nutrients and fluid replacement have a role in preparation, support and enhancement of the athlete’s exercise and sports performance. An adequate sports diet also prevents some negative effects associated with prolonged exercise, such as nutrient fatigue. The nutrients, namely, carbohydrates, proteins and fats provide energy for exercising muscles. The proportion of these nutrients required are dependent on factors such as the athlete’s body weight, age, gender, intensity and duration of exercise and timing of meals (i.e. eating before, during and after training or competition). While many athletes believe they are eating a high-carbohydrate, low-fat eating plan, on closer inspection or analysis of the diet it is often revealed that the diet is in fact a high-fat, low-carbohydrate plan, and not much different to the average western diet. Participation in exercise may also increase the need for certain vitamins and minerals, those that have specific functions in exercise metabolism and the immune system.

All athletes start out with recreational exercise. Some may continue this level of exercise participation indefinitely. However, for many athletes, participation in sport can become highly competitive and this environment requires that athletes train and compete at their maximum capacity. The need for an adequate sports diet can help athletes sustain strenuous activities that may be of varying intensity, duration, frequency and skill.

To help an athlete achieve an adequate sports diet, the goals set out in the following text can be applied to all athletes participating at any level of sport. These goals form the foundation of the athlete’s everyday diet, which can then be tailored to suit the individual needs of an athlete as their demand for food and fluid change through various stages of training, competition and recovery.

Goals of an adequate sports diet

• To follow the basic healthy eating guidelines
• To meet energy and nutrient requirements
• To maintain health and well-being in both short term and long term
• To reach and maintain a healthy body mass, appropriate body composition levels, including body fat and body muscle tissue, and body water, as well as other health indices (i.e. waist circumference).
• To plan and implement training and competition nutrition strategies
• To ensure optimal hydration before, during and after exercise
• To treat suboptimal nutrient levels and any known nutritional deficiencies
• To treat and manage any ailments or diseases (i.e. diabetes) while eating for sport
• To determine if or when nutritional supplements may be of benefit to the diet and exercise performance

Barriers to achieving an adequate sports diet and best food practice

Although athletes are constantly seeking ways to improve exercise performance, there may be a number of reasons that may prevent athletes from choosing or adhering to an adequate sports diet or adjusting their dietary behaviour to achieve optimum performance. The following will be discussed in the subsequent text:

• Athletes’ source of information (i.e. the media) and misconceptions about optimal sports nutrition practices
• Poor nutrition knowledge
• Dietary extremism
• Poor practical food skills
• Frequent travel

Athletes’ primary source of information and misconceptions

There is a plethora of information available through the media, and surveys on athletes have found that many athletes rely on the media as the primary source of nutrition information (Jacobson and Aldana, 1992). Thus at the time, TV, commercials, magazines, advertisements, books, popular magazines and newspapers appeared to be a source of nutritional information for athletes. Another media forum, the Internet, has become accessible and affordable to athletes. Various social networking websites allow users to exchange information by chat-room forums, email and instant messaging, some allowing content to be distributed in ‘real-time’ as it is uploaded. Facebook, Bebo and Twitter are among the popular online social networks.

However, not all forms of information are credible or substantiated by scientific evidence (also referred to as evidence-based information), and may lead to confusion for many athletes. This confusion may be one reason why athletes lack understanding in this specialised science of sport and exercise nutrition. It is advisable that athletes educate themselves about sources of valid and reliable information, try to access nutritional support programmes that are available to them or seek the advice or counselling of a qualified sports dietitian or sports and exercise nutritionist if they require specialist dietary advice.

Poor nutrition knowledge

Since knowledge, attitudes and beliefs may act to encourage or discourage behaviour change (Thompson and Byers, 1994; Main and Wise, 2002), lack of knowledge about sports nutrition may be a barrier for athletes who wish to follow an adequate sports diet and make favourable dietary choices. It seems that while some athletes may perceive themselves to have an understanding of nutrition for athletes, their perception may not match their performance in a knowledge survey. With the rise in over-drinking during exercise, a recent survey examined how ‘beliefs about hydration and physiology drive drinking behaviours in runners’. Winger et al (2011) found that most runners relied on personal experience of ‘trial and error’ as a factor influencing their drinking behaviour. However, the survey revealed this group of athletes’ inadequate understanding of physiological principles underlying hydration practices, putting them at risk over-hydration and its consequences.

Some athletes may have a general nutrition knowledge base, but fair poorly when asked questions specifically about the diet for athletes. Most athletes in recent surveys have been unable to identify the role of sport-specific nutrients such as carbohydrates and its role in exercise (Dunn et al, 2007), and/or proteins as a fuel for exercise. The latter misconception, that protein is a primary source of energy for muscle contraction, is a common finding among athletes surveyed (Zawila et al, 2003; Condon et al, 2007; Rash et al, 2008). It is, therefore, not surprising when athletes regard protein supplementation as necessary for exercise performance (Rosenbloom et al, 2002; Rash et al, 2008).

Not all athletes have poor nutrition knowledge, as certain groups of athletes appear to have a higher level of knowledge in nutrition. Apart from having a few misconceptions, elite athletes competing at national level, scored higher on nutrition-related multiple-choice, general knowledge and sport-specific questions than their age-matched non-athletes (Cupisti et al, 2002). Similarly, Raymond-Barker et al (2007) found that competitive endurance athletes’ level of knowledge of general nutrition was significantly higher than non-athletes of the same age group and gender.

What knowledge would benefit athletes?

Athletes need to understand the concepts in energy and fluid balance. In general these include, but are not exclusively:

• energy and its terms, i.e. kilocalorie, kilojoule;
• their individual energy expenditure and energy intake, and the relationship between dietary intake and physical performance;
• proportion of nutrients in the diet, i.e. percentage of carbohydrate, protein and fat. That is, do athletes know what a 60% carbohydrate-rich diet means?
• the nutrient carbohydrate, and glycaemic index and sport;
• the nutrient protein, amino acids and the required amount and effects of excessive intake;
• the nutrient fat and requirements for sport, fat adaptation diets and their effects;
• the nutrient water and the fine balance between dehydration and over-hydration in sport and the consequences thereof;
• the nutrient alcohol and its impact on sports performance and recovery;
• vitamins, minerals, dietary allowances and their role in health and exercise; and
• antioxidants, muscle soreness and requirements for athletes of various sports.

Athletes may not be able to practically apply their nutrition knowledge to make favourable food choices, due to the following reasons:

• Some may have a misunderstanding of food groups, or pictorial food guides like the Eatwell Plate (UK), MyPlate (USA) or the food pyramid guides, and its basic dietary guidelines. For example, the athletes surveyed by Dunn et al (2007) had problems translating nutrition knowledge into food choices as only half the questions about food choices were correctly answered. Furthermore, with a mean score of 36 points (out of 67) for the section on food groups, merely a third of athletes knew how many servings of fruits and vegetables are recommended daily. It is like having a few pieces of the puzzle but not being able to see the whole picture.
• Other studies have also shown that while athletes may have the knowledge, or know what advisable eating behaviour is, favourable dietary practices may not be applied (Nichols et al, 2005; Robins and Hetherington, 2005).
• An inability to understand the profile of foods within food groups, i.e. those foods within one food group have a similar, not identical nutrient make-up. For example, pasta, potatoes and bread are all starch that contain carbohydrates and have a similar nutrient profile when it comes to macronutrients (carbohydrate, protein and fat content). However, when it comes to micronutrients, a potato is rich in Vitamin C, potassium and copper, while pasta is a good source of Vitamin B2 (riboflavin) and manganese and copper. Brown and wholemeal bread contains Vitamin B1 (thiamin) and B2 (niacin), and minerals iron, magnesium, copper and others. Therefore, while each serving of pasta, potato and bread yields similar amounts of carbohydrate, protein, fat and likely copper, the rest of the micronutrient contribution is quite different. That is why it makes sense to have a variety of foods within a food group. If a person just eats pasta and avoids potatoes and bread, they miss out on these foods that are rich in iron, magnesium, manganese and fibre. If the pattern persists over weeks or months, they can be at risk of suboptimal nutrient levels that can eventually lead to nutrient deficiencies.
• An inability to read food labels and choose the most appropriate packaged food or supplement as part of an adequate sports diet. In urban areas where there is no lack of access to processed and packaged food, athletes are bombarded with branding, nutritional claims, symbols of endorsement, ingredient lists and nutritional information. If they are not guided by what to look for to meet their individual health and exercise performance goals, they may fall prey to clever marketing and advertising of food companies, retailers and anecdotes of other athletes.
• Not knowing how to interpret and use dietary reference values (DRV), like recommended nutrient intakes (RNI), or guideline daily amounts (GDA) in their individual diets.

Athletes may not be able to convert scientific sports nutrition principles into achievable dietary practices because they do not know:

• about their body weight loss (through sweat) or gain (through over-drinking) during exercise and its impact on their health and performance;
• about ergogenic aids (performance-enhancing aids) and its uses;
• about pre-, during and post-competition nutrition strategies;
• about sport-specific nutritional needs, i.e. fluid strategies to use in endurance sports.

Dietary extremism

Athletes who have misconceptions about nutrition and sports performance may be trapped by di...

Table of contents

• Cover
• Dedication
• Title Page
• Copyright
• Preface
• Acknowledgments
• Foreword
• Chapter 1: Introduction
• Chapter 2: The Athlete’s Energy Needs
• Chapter 3: Laying the Foundation of a Good Diet
• Chapter 4: Carbohydrates
• Chapter 5: Protein
• Chapter 6: Fats
• Chapter 7: Vitamins and Minerals
• Chapter 8: Fluid Balance
• Chapter 9: Performance-Enhancing (Ergogenic) Aids
• Appendix: Reference Values for Estimated Energy Expenditure
• Glossary
• Student Exercises
• Answers to Student Exercises
• References
• Internet Resources
• Index