Form of Dairy Products on Satiety, Food Intake and Post-meal Glycaemia in Young and Older Adults

The proposed study is planned to determine the potential role for regular fat dairy products in short-term metabolic control in younger and older adults and the metabolic flexibility in response to food components, which are areas that have not yet been explored. Subjects would be served with solid (cheese), semi-solid (yogurt) and liquid (milk) dairy products and skim milk (control) and water (non-caloric control) in three separate studies.

Over the last 30 years, overweight and obesity have become characteristic of the majority of Canadians. Approximately 60% of adults in Canada are overweight or obese. The Canadian Health Measures Survey, conducted during 2007-2009, estimated prevalence of metabolic syndrome at 19.1% in the adult population. In addition, according to the 2010 Canadian Community Health Survey, 18.1% of Canadian adults have been reported obese. Along with the health burden, it has also brought about an estimated economic burden of $ 4.3 billion annually in 2001, which has likely doubled as of today.

Metabolic syndrome and type 2 diabetes occur concurrently with insulin resistance marked by increased blood glucose levels at fasting and postprandial, glycosylated blood proteins leading to arterial damage, inflammation and comorbidities such as cardiovascular disease. Despite increased consumer interest in consuming foods that may help treat or prevent obesity and diabetes, effective countermeasures against metabolic diseases have yet to be established. Thus, food products that are capable of controlling parameters of metabolic diseases including blood glucose, insulin levels and food intake are in urgent need of investigation and identification. Dairy products are believed to hold this potential because of their functional physiological properties.

There have been many observational and long-term clinical studies showing that regular consumption of dairy products correlate with a better body composition and a lower incidence of obesity and type 2 diabetes. Studies have also found that dairy proteins are more satiating than other types of proteins, and that they are effective in lowering the increase in glycemic response after high GI food intake, but most studies have been done in isolated proteins. Hence, the role of dairy proteins, in their conventional food form reflecting usual intake, on food intake and glycemia and their interactions with these metabolic diseases is of interest.

From short-term studies done in our lab, the investigators have shown that dairy products can bring about benefits in glycemic control and food intake when consumed before or within ad libitum meals, which can be achieved by both insulin dependent and independent mechanisms. The investigators have shown that fluid milk products and yogurt improve post-meal glycemic excursions when consumed before or within an ad libitum meal by healthy young adults. Except the yogurt study conducted in our lab, there have been no other studies reporting the role of solid or semi-solid dairy products consumed before a meal, within a meal, immediately post-meal or as between meal snacks on glycemia and appetite control. Our study on yogurt showed that yogurts, especially those with high protein to carbohydrate ratio, reduced pre-meal glucose incremental areas under the curve. Further studies on solid and semi-solid dairy need to be conducted because milk, like other caloric beverages, lead to calorie accumulation if consumed before or with a meal even though it provides more nutrients, lowers post-meal blood glucose excursions and leads to greater post-meal satiety in young adults.

Moreover, the evidence appears to be relatively consistent with respect to a beneficial role of low-fat dairy products in the prevention of type 2 diabetes (T2D), however, the role of regular/high-fat dairy is less clear. A number of cross-sectional and prospective epidemiological studies have identified a positive association between the intake of dietary fat and the risk for development of either insulin resistance or T2D20. More research is needed to better understand the role of regular-fat dairy products on food intake as well as of glycemic control.

Three studies are proposed:

* Study 1 investigates the effects of 2-servings of pre-meal regular fat; cheese, yogurt and milk on food intake at 2 hours, satiety and glycemia in normal weight young adults (20-30 yrs) and normal weight/overweight older adults (60-70 yrs).
* Study 2 investigates the effects of 1-serving of pre-meal regular fat; cheese, yogurt and milk on satiety and glycemia in normal weight young adults (20-30 yrs) and normal weight/overweight older adults (60-70 yrs).
* Study 3 investigate the effects of 1 serving for pre-meal regular fat; cheese, yogurt and milk on food intake at 15 min and 30 min, satiety and glycemia in normal weight/overweight older adults (60-70 yrs).

Eligibility Criteria:
Inclusion Criteria:

* Healthy, non-smoking male and female participants aged 20-30 and 60-70 years old
* Young adults with body mass index (BMI) of 18.5-24.9 kg/m2 (normal weight) and older adults with BMI between 18.5-29.9 kg/m2 (normal/overweight).

Exclusion Criteria:

* Diabetic
* Individuals on medication affecting appetite
* Lactose-intolerant or allergic to dairy (including milk, yogurt, and cheese)
* Breakfast skippers
* Gastrointestinal problems
* Individuals on an energy-restricted diet