HEALTH PROFESSIONALS

Sugars and Health

Physical Activity

Physical activity is defined by the World Health Organization (WHO) as as “any bodily movement produced by skeletal muscles that requires energy expenditure”.

Participation in regular physical activity can help manage body weight, improve health, and reduce the risk of developing many chronic diseases. These benefits can be achieved as part of a balanced lifestyle that includes healthy eating.

• Physical Activity Recommendations
• Benefits of Physical Activity
• Physical Activity Trends in Canada
• Carbohydrates for Healthy Active Living
• Carbohydrates for Athletes
• References

Physical Activity Recommendations

Adults and Older Adults

Health Canada, in cooperation with the Canadian Society for Exercise Physiology, recommend 30-60 minutes of activity each day as part of the Canada’s Physical Activity Guide to Healthy Active Living and Canada’s Physical Activity Guide to Healthy Active Living for Older Adults.  The duration of exercise is dependent on the intensity of the exercise (see Table). The Guide specifically recommends a variety of exercises including endurance exercise (4-7 days/week), flexibility exercise (4-7 days/week), and strength exercise (2-4 days/week).

The US Institute of Medicine and Health Canada also released a set of recommendations on physical activity as part of the Dietary Reference Intake (DRI) Report on Macronutrients. Similar to Canada’s Physical Activity Guide, the report recommends 60 minutes of daily moderate intensity physical activity (e.g., walking/jogging at 4.8 - 6.4 km per hour) or shorter periods of more vigorous exertion (e.g., jogging for 30 minutes at 8.9 km per hour).  This is in addition to the activities required by a sedentary lifestyle (such as walking to the bus). In general, by increasing the duration, intensity and/or frequency of physical activity, greater health benefits may be achieved.

Children and Youth

Health Canada and the Canadian Society for Exercise Physiology developed Canada’s first set of physical activity guidelines for children and youth in 2002 as part of Canada’s Physical Activity Guides for Children and Youth.  In the Guides, children and youth are advised to increase the time they currently spend on physical activity by 30 minutes per day, and progress over approximately 5 months to at least 90 minutes ofdaily activity including both moderate activities (such as brisk walking, skating or bike riding) and vigorous activities (such as running or soccer). The DRI Report recommends at least 60 minutes or more of activity every day, noting that “children in the active and very active categories are most likely participating in moderate and vigorous activities, in addition to walking at 2.5 mph”. 

Back to top »

Benefits of Physical Activity

Regular physical activity plays a key role in chronic disease prevention and weight maintenance.  More specifically, physical activity is associated with the prevention of heart disease, stroke, diabetes, osteoporosis, and some cancers and can help to alleviate symptoms of depression. Many of the benefits of physical exercise are exerted through improved glucose metabolism, altered lipid profiles, a reduction in body fat (total and abdominal), and lowered blood pressure.

Regular physical activity can also have additional benefits. For young Canadians, physical activity encourages optimal growth and development and can help build positive self-esteem. For older Canadians, physical activity can help sustain independent living and can lead to improvements in quality of life.   

Back to top »

Physical Activity Trends in Canada

Since 2000, Health Canada, Statistics Canada and the Canadian Institute for Health Information have jointly conducted the Canadian Community Health Survey (CCHS). The CCHS operates on a two-year data collection cycle that comprises two types of surveys; a general health survey of approximately 130,000 Canadians takes place in the first year of the cycle and a focused topic survey takes place in the second year of the cycle on a smaller sample (35,000) of Canadians. Leisure-time physical activity levels are monitored during the general health survey.

The CCHS surveys define being physically active as expending greater than 3.0 kcal/kg/day, equivalent to about 1 hour of walking daily. This level of activity is required to achieve optimal health benefits.  Moderately active is defined as expending 1.5-2.9 kcal/kg/day and expending <1.5 kcal/kg/day is considered inactive (see Table).

According to the 2007 CCHS survey, almost half of Canadians over the age of 12 are considered inactive. Furthermore, there is a trend towards lower levels of activity with increasing age. Over two-thirds of Canadians aged 12-19 are active or moderately active, while only 40% of adults over the age of 65 fall into these categories. Physical activity levels also vary by province with the highest proportion of active or moderately active people in the Yukon (55%) and British Columbia (54%) compared to Nunavut (40%) and New Brunswick (43%). Nationally, slightly more men are active than women.

Children and Youth

In addition to the CCHS, other Canadian surveys conclude that children and youth are not meeting current recommendations for physical activity. Canada’s Physical Activity Guides for Children and Youth recommends 90 minutes of activity each day, which translates into approximately 16,500 steps per day. The Canadian Fitness and Lifestyle Research Institute (CFLRI) CANPLAY study (2005-2008) however, found that children and youth aged 5-19 took an average of 11,950 steps each day. The number of steps taken by children decreased with increasing age. Healthy Active Kids Canada also found that 90% of children and youth are not meeting Canada’s physical activity guidelines of 90 minutes a day as reported in their 2009 Report Card.

The CFLRI’s 2005 Physical Activity Monitor reported that 72% of children ages 5-17 participate in sport (competitive, structured; non-competitive, structured; non-competitive, non-structured).  However, the percentage of Canadian children participating regularly in organized sports activities is declining, based on the findings of the General Social Survey conducted by Statistics Canada (1995-2005).

Back to top »

Carbohydrates for Healthy Active Living

Eating Well with Canada’s Food Guide is designed to meet the nutrient and energy needs for sedentary Canadians. Active Canadians may require higher intakes of energy and certain nutrients, such as carbohydrate, than recommended by the Guide. The DRI report recommends that all Canadians consume 45 to 65% of their total calories from carbohydrate. This range ensures sufficient intakes of essential nutrients and is based on evidence that suggests a role for carbohydrates in the prevention of chronic disease.

Dietary carbohydrate (sugars and starches) is digested and absorbed and the resultant monosaccharides, specifically glucose, are used by a variety of tissues for energy or stored in muscles and the liver as glycogen. During exercise, the active muscle relies heavily carbohydrate-derived energy sources (muscle and liver glycogen, blood glucose) and also on lipid-derived fuel (fatty acids, intramuscular triglyceride). The duration and intensity of exercise determines which fuel is the primary source of energy.

During low intensity exercise, the body gets a greater proportion of its energy from fatty acids. As the intensity of exercise increases, so does the percentage of energy derived from carbohydrate. Muscle glycogen provides the primary source of energy, with a smaller contribution from blood glucose and muscle lactate (a by-product of glycogen metabolism). As glycogen levels decline, there is a greater reliance on blood glucose levels. If blood glucose levels cannot be maintained, the intensity of the exercise will decrease. Under these circumstances, dietary carbohydrate is required.

For more information on carbohydrate for healthy active living, please click here

Back to top »

Carbohydrates for Athletes

Training Diet

It is the position of the American Dietetic Association (ADA), Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM) that “physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition”. It is recommended that athletes consume 6 -10 grams of carbohydrate/kg/day depending on the type of activity (including duration and intensity), total energy expenditure, environmental factors and sex. For example, a 68 kg (150 lb) male athlete training vigorously for 2 hours a day should consume about 2400 kcal per day from carbohydrate sources, or 69% of total calories. A female endurance athlete weighing 57 kg (125 lbs) also training for 2 hours a day should consume about 2000 kcal per day from carbohydrate sources, or 80% of calories [(Calculations based on 8.8 g CHO/kg/day; 44kcal/kg (female), 51kcal/kg (male)].

Before the event

Traditionally, athletes utilized “carbohydrate loading” over the 3 days prior to an event to maximize glycogen stores in the muscle. This classic method exhausted glycogen stores through intense exercise coupled with a low-carbohydrate diet.  When glycogen stores were depleted, a high carbohydrate diet would then be consumed (>90% of total kcal).  Athletes often experienced hypoglycemia, irritability, and chronic fatigue by adhering to this regime. More recently, experts recommend daily ingestion of high-CHO meals (~65% CHO) to maintain muscle glycogen, while increased ingestion rates are employed (~70% CHO) in the 5 – 7 days leading up to competition as a means of maximizing muscle and liver glycogen stores and in order to sustain blood glucose during exercise.

Day of the event

Exercise performance can be improved by eating prior to exercising, rather than exercising in the fasted state. Pre-exercise meals or snacks may enhance carbohydrate availability by increasing muscle and liver glycogen stores, or by providing a source of glucose in the gut for later release. Controversy exists regarding when a pre-event meal should be consumed as well as the amount and type of carbohydrate it should contain.  In general, a pre-event meal or snack should be relatively low in fibre and fat, moderate in protein, and high in carbohydrate. According to DC, ADA & ACSM, performance may be enhanced by consuming 200 -300 g of carbohydrate, 3 - 4 hours before exercise.  Data regarding the impact of the glycemic index (GI) of the pre-event meal on athletic performance is inconclusive.

During the event

The purpose of consuming carbohydrate during exercise is to maintain plasma glucose concentration, sustain high rates of carbohydrate oxidation and spare liver glycogen. For activities longer than 60 minutes in duration, DC, ADA & ACSN recommend consuming 30 - 60 grams of carbohydrate per hour in small, frequent intervals. These carbohydrates should have a moderate to high GI such as sports drinks, juice or energy bars. The need for carbohydrate (and electrolytes) during exercise will depend on the intensity, duration and weather conditions. Generally, consuming only water is generally sufficient for activities lasting less than 60 minutes. However, athletes may still benefit from carbohydrate consumption during these shorter activities if they are extremely intense or if they are occurring after an overnight fast.

After the event

The goal of post-exercise nutrition is to replace the muscle glycogen, fluid and electrolytes lost during exercise and to aid in muscle recovery.  In the two hours post exercise, muscles can store glycogen at an accelerated rate. Therefore, DC, ADA & ACSN recommend consuming 1.0 -1.5 g/kg in the first 30 minutes after competition repeated every 2 hours for 4-6 hours, particularly if an athlete will be competing again within the next 24 hours. If no competition is scheduled, muscle glycogen will recover with high (7-10g/kg) carbohydrate intakes over the next 24-36 hours. The type of carbohydrate consumed also appears to influence post-exercise glycogen synthesis. Glucose and sucrose seem equally effective when consumed as recommended above; fructose alone is less effective.  There is some evidence to suggest that consuming carbohydrate foods post-exercise with moderate or high GI produces higher muscle glycogen stores than the same amount of low GI carbohydrates.

For more on the glycemic index, please see The Glycemic Index: Clinical and Public Health Significance. (PDF Format)

Here is a summary of the carbohydrate requirements for athletes before, during, and after a competition:

Back to top »

References

Canada’s Physical Activity Guide for Children and Youth, Health Canada, 2002

Canada’s Physical Activity Guide to Healthy Active Living, Health Canada, 1998

Canada’s Physical Activity Guide to Healthy Active Living for Older Adults, Health Canada, 1999

Canadian Community Health Survey, Statistics Canada, 2000/2001, 2003, 2005 and 2007

Carbohydrates and fat for training and recovery. Burke LM et al. Journal of Sports Sciences 2004; 22:15-30.
Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients), Institute of Medicine, National Academy Press, 2005

Fuel for Your Activity, Canadian Sugar Institute, 1998

General Social Survey , Statistics Canada, 2005

Global Strategy on Diet, Physical Activity and Health , World Health Organization

Glycemic Index of Popular Sports Drinks and Energy Foods . Gretebeck RJ et al. Journal of the American Dietetic Association, 102 (3): 415-417, 2002

Guidelines for Carbohydrate Intake: Do Athletes Achieve Them? Burke L et al. Sports Medicine 31(4): 267-299, 2001

International Society of Sports Nutrition position stand: Nutrient timing, Kerksick et al. Journal of the International Society for Sports Nutrition, Oct 3; 5:17, 2008

Physical Activity and Sport Monitor, Canadian Fitness & Lifestyle Research Institute, 2005

Position on Nutrition and Athletic Performance. Dietitians of Canada, American College of Sports Medicine, American Dietetic Association. Medicine & Science in Sports Exercise, 2009 Mar; 41(3):709-31

Back to top »