Overweight and Obesity

Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. One crude measure is body mass index (BMI), which uses an individual’s height and weight to determine a numerical value. According to this measure, an individual with a BMI >25 is considered to have overweight, and an individual with a BMI >30 is considered to have obesity (1).

  • Obesity is a Complex Disease. There are many different risk factors for obesity and weight gain, including dietary habits, level of physical activity, gut (microflora) health, environmental factors, sleep patterns, stress, and genetics.
  • Diet and Obesity. Research suggests eating too many calories from all sources – sugars, starches, proteins, fats, and alcohol – and not using these calories through normal body functions, movement, and physical activity can contribute to weight gain as the excess calories are instead stored in the body as fat.
  • Sugars and Obesity. Studies have shown varying results. Overall, research suggests that when energy intake is controlled, weight is maintained, regardless of the source of calories. 
  • Weight Management. Foods and beverages higher in sugars and fats are often key sources of excess calories. Diet modifications, such as reducing the frequency or portion size of these types of foods, and increasing consumption of nutrient-dense foods like fruits and vegetables, can help reduce intake of excess calories. 

Obesity is a Complex Disease

Having excess weight increases the risk of developing a number of chronic diseases, such as type 2 diabetes and cardiovascular disease.

Obesity is caused by societal influences, individual psychology and activity, biology, food consumption, food production, activity environment

There are many factors that contribute to the risk of obesity including biology (e.g. your genetics), diet (e.g food consumption), individual activity (e.g. physical activity), individual psychology (e.g. stress), activity environment, societal influences, and food production.

Diet and Obesity

Diet is one factor that may increase risk for overweight or obesity. An individual may experience weight gain when more energy (calories) is ingested from all foods and beverages than is expended for normal bodily functions (e.g., breathing, digestion, pumping blood), and daily movement and physical activity (2). Fluctuations in energy balance (higher or lower energy intake relative to expenditure) within a meal, day or week are normal and will not necessarily lead to a persistent change in body weight. However, large increases in energy intake relative to expenditure (i.e., positive energy balance) at regular intervals or small consistent increases over a long period of time can result in weight gain, and potentially lead to obesity.

All food and beverage sources of protein, carbohydrate (sugars and starches), fat, and alcohol contribute calories. Research suggests eating too many calories from all sources – sugars, starches, fats, proteins, and alcohol – can contribute to weight gain (3) as the excess calories from these nutrients are not used and instead stored as fat.

Energy balance is key to maintaining a healthy weight

Sugars and Obesity

Obesity rates among children and adults in Canada have increased substantially during the past 25 years, according to the 2015 Statistics Canada Canadian Community Health Survey, which directly measured the height and weight of a nationally representative sample of over 30,000 people. Based on data from Statistics Canada, higher consumption of calories independent of the sources increased the risk of obesity. 

Sugars does not cause obesity; too many calories from all foods can lead to weight gain

However, trends in sugars consumption in Canada plotted against rates of obesity indicate an inverse relationship; as rates of obesity continue to increase, consumption of added sugars has declined.

Obesity paradox - added sugars consumption falling while obesity rates rise in Canada

Added sugars based on Statistics Canada availability data; obesity rates determined by body mass indices.

Results from research examining the effect of sugars on obesity have shown varying results:

  • A number of meta-analyses and reviews concluded that when the amount of sugars in the diet is either increased or decreased, there is a corresponding change in weight. However, when sugars are replaced with other carbohydrates, resulting in a maintenance of total overall energy intake, there is no change in body weight (3-5).
  • When sweetened beverages are added to a diet, weight gain is often observed. When sweetened beverages are removed, weight loss is observed, demonstrating the impact of the addition and subtraction of calories on body weight (6-8); but when energy intake is controlled there is no change in body weight (9).

Weight Management

In order to reduce the risk of overweight or obesity, some individuals can choose to address lifestyle factors such as diet and physical activity. From a diet perspective, talking to a physician or a registered dietitian may be helpful to determine how many calories are needed for each individual per day.  Getting enough sleep and incorporating physical activity into daily routines can also help maintain a healthy weight. Additional suggestions related to diet include:

  • Selecting nutrient-dense whole foods more often, including whole fruits and vegetables, whole grains, legumes, and lean meats instead of other options (such as sugar sweetened beverages, processed foods, and meats high in fat).
  • Reducing the portion size and/or frequency that higher calorie snacks such as cakes and pastries, chocolate and candies, cookies and granola bars, doughnuts and muffins, ice cream and frozen desserts, French fries, potato chips, nachos and other salty snacks are consumed. These foods can be enjoyed as occasional treats rather than every day.
  • Water is a zero calorie beverage option for hydration and to quench thirst.
  • Sugar sweetened beverages can also be enjoyed. In order to reduce the calories in these beverages, individuals could:
    • Mix sweetened carbonated drinks with club soda or mineral water
    • Add lemon wedges or small amounts of 100% fruit juice to water to provide variety in flavour.
  • Sugars and fats in pre-prepared hot and cold coffee and tea drinks add calories; choosing plain coffee or tea and adding milk and/or a small amount of sugar to suit individual tastes can reduce calories for the day.
For more information, additional resources include: 
Recent news items include: 
  1. World Health Organization. 2018. Obesity
  2. Centers for Disease Control and Prevention. 2018. Adult Obesity Causes and Consequences.
  3. Te Morenga L et al. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013;346:e7492.
  4. Rippe JM and Angelopoulos TJ. Relationship between added sugars consumption and chronic disease risk factors: current understanding. Nutrients. 2016;8(11):697.
  5. Khan TA and Sievenpiper JL. Controversies about sugars: Results from systematic reviews and meta-analyses on obesity, cardiometabolic disease and diabetes. EJCN. 2016;55(2):25-43.
  6. Ma J et al. Sugar-sweetened beverage consumption is associated with change of visceral adipose tissue over 6 years of follow-up. Circulation. 2016;115.
  7. Malik VS et al. Sugar-sweetened beverages and weight gain in children and adults: a systematic review and meta-analysis–. AJCN. 2013;98(4):1084-102.
  8. Kaiser KA et al. Will reducing sugar‐sweetened beverage consumption reduce obesity? Evidence supporting conjecture is strong, but evidence when testing effect is weak. Obesity Reviews. 2013;14(8):620-33.
  9. Trumbo PR, Rivers CR. Systematic review of the evidence for an association between sugar-sweetened beverage consumption and risk of obesity. Nutrition Reviews. 2014;72(9):566-74. T