HEALTH PROFESSIONALS

Sugars and Health

Physical Activity

Physical activity is defined by the World Health Organization (WHO) 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

With support from the Public Health Agency of Canada, the Canadian Society for Exercise Physiology (CSEP) released updated physical activity guidelines for Canadians in 2011. The Canadian Physical Activity Guidelines are designed to help promote physically active lifestyles in order to improve health, increase vigour, prevent disease, and get the most out of life.

For Adults (18 – 64) - Canadian Physical Activity Guidelines for Adults 18 – 64 Years recommend accumulating at least 150 minutes of moderate to vigorous intensity aerobic physical activity per week, in bouts lasting at least 10 minutes or more. Activities can be accumulated throughout the day. The Guidelines add that it is beneficial to include muscle and bone strengthening activities using major muscle groups, on at least 2 days per week.

For Older Adults (65 years & older) - Canadian Physical Activity Guidelines for Older Adults are the same as those for Adults aged 18 – 64; however it is recommended that those with poor mobility perform physical activities to enhance balance and prevent falls.

The Physical Activity Guidelines encourage individuals to participate in a variety of forms of exercise (e.g. aerobic, strengthening) to achieve health benefits.

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. 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

For Children (5 – 11) - For optimal health and development, Canada's Physical Activity Guidelines for Children recommend that children aged 5 – 11 should accumulate at least 60 minutes of moderate to vigorous intensity physical activity daily. This should include vigorous intensity activities at least 3 days per week (running, swimming) and muscle and bone strengthening activities at least 3 days per week.

For Youth (12 – 17) – For optimal growth and development, Canada's Physical Activity Guidelines for Youth recommend that youth aged 12 – 17 engage in at least 60 minutes of moderate to vigorous intensity physical activity daily. It is recommended that youth include at least 3 days per week of vigorous intensity activities (soccer, swimming) and at least 3 days per week of muscle and bone strengthening activities.

These guidelines are in accordance with the DRI Report.

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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. Benefits of physical exercise include improved glucose metabolism and lipid profiles, a reduction in body fat (total and abdominal), and lowered blood pressure. 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.   

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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 is comprised of two types of self-report surveys: an annual general health survey of approximately 130,000 Canadians and a focused survey of a smaller sample (35,000) of Canadians. The general health survey also monitors the leisure-time physical activity levels. The focused survey covers specific health topics and is conducted every 3 years.

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 would be equivalent to walking at least 30 minutes a day or taking an hour-long exercise class at least 3 times a week. Expending <1.5 kcal/kg/day is considered inactive (see Table).

In the 2010 CCHS survey, 52% of Canadians reported that they were at least “moderately active.”

In 2007, Statistics Canada, in partnership with the Public Health Agency of Canada and Health Canada, launched the Canadian Health Measures Survey (CHMS). CHMS tracked Canadians’ physical activity levels from 2007 to 2009 using accelerometers, which participants wore for one week. According to CHMS data, only 15% of Canadian adults accumulated the recommended 150 minutes of moderate- to vigorous physical activity per week. Almost half (47%) were active for less than one day per week; 53% were active for 30 minutes one or more times a week. Obese men and women were less physically active than those at a healthy weight.

The CHMS results published in 2011 were surprising as they found physical activity patterns of adults to be much lower compared to the CCHS survey findings (15% versus 52% respectively). The CHMS was the first study to measure Canadians’ actual physical activity, rather than rely on CCHS self-reported surveys.

Both CCHS and CHMS surveys indicated that men tended to be more physically active than women and that physical activity levels declined with increasing age.

Children and Youth

Many Canadian surveys conclude that children and youth are not meeting the current recommendations for physical activity. The Canadian Physical Activity Guidelines for Children and Youth recommends 60 minutes of activity each day, which translates into approximately 13,500 steps per day. However, data from the CANPLAY study showed that children and youth aged 5-19 took an average of 11,600 steps each day and the number of steps taken declined with increasing age.

Data from the Canadian Health Measures Survey reported that only 7% of children and youth met the physical activity guidelines of 60 minutes of activity at least 6 days a week; 44% of children and youth met the guidelines 3 days a week. Considerably higher percentages of kids accumulated 30 minutes of activity a day: 25% did so at least 6 days a week and 78% got 30 minutes at least 3 days a week.

In 2010, the Physical Activity Monitor reported that 75% of Canadian children aged 5-17 participated in sport (competitive, structured; non-competitive, structured; non-competitive, non-structured). This proportion has not changed significantly since 2005. Though the percentage of Canadian children and youth participating in organized sport appears to be high, disparities persist. More boys (81%) than girls (70%) participated in sports; sports participation was also higher among children and youth who came from higher income and more highly educated families, or whose parents also participated in sports. 

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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

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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:

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References

Canada Report Card on Physical Activity for Children and Youth. Active Healthy Kids Canada, 2011.

Canadian Physical Activity Guidelines for Children. Canadian Society for Exercise Physiology, 2011.

Canadian Physical Activity Guidelines for Youth. Canadian Society for Exercise Physiology, 2011.

Canadian Physical Activity Guidelines for Adults, Canadian Society for Exercise Physiology, 2011.

Canadian Physical Activity Guidelines for Older Adults. Canadian Society for Exercise Physiology, 2011.

Canadian Community Health Survey, Statistics Canada, 2000/2001, 2003, 2005. 2007, 2008, 2009, 2010.

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, 2011

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

The Glycemic Index: Clinical and Public Health Significance, Canadian Sugar Institute, 2008.

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

2010 Physical Activity and Sport Monitor, Canadian Fitness & Lifestyle Research Institute, 2011

Physical Activity Levels of Canadian Children and Youth. Canadian Fitness & Lifestyle Research Institute, 2011.

Physical activity of Canadian adults: Accelerometer results from the 2007 to 2009 Canadian Health Measures Survey. Colley RC et al. Statistics Canada Health Reports 2011;22(1).

Physical activity of Canadian children and youth: Accelerometer results from the 2007-2009 Canadian Health Measures Survey. Colley RC et al. Statistics Canada Health Reports 2011;22(1).

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

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