The Apple Study: Investigating the Effects of Whole Apple Consumption on Risk Factors for Chronic Metabolic Diseases in Overweight and Obese Adults

Obesity is characterized by an underlying inflammatory state in which various inflammatory signaling molecules, termed cytokines, affect metabolic processes central to type 2 diabetes and cardiovascular disease; leading causes of disability and death in Ontario. Such obesity-associated inflammation is partly due to the movement of endotoxin (i.e. lipopolysaccharide (LPS), a cell wall component of Gram-negative bacteria) from the gut microbiota to the blood, resulting in elevated blood levels of LPS (a condition termed metabolic endotoxemia) that stimulates inflammation. Digestion of a high-fat meal increases blood LPS and is subsequently associated with inflammation and metabolic impairments. However, in this context, little is known about how the consumption of bioactive-rich foods, such as whole apples, can improve impaired inflammatory and metabolic responses in overweight and obese individuals. Apples are a key commodity to study given that they are Ontario's predominant fruit crop with the apple industry valued at approximately $400 million, they require little food preparation, and they are common in the diet year-round. There are some, but limited, reports of potential apple-induced health benefits related to reductions in inflammation and improved metabolic responses in lean/healthy individuals, but work in overweight and obese individuals is especially lacking. Thus, to address the gap in our understanding of how daily apple intake may improve the health consequences of obesity, we will conduct a randomized clinical trial in which overweight and obese adults will consume three Ontario-grown Gala apples (approximately 300 g) as part of their typical diet in one sitting (i.e. acute consumption) and/or daily for six weeks (i.e. chronic consumption). The Acute Apple Consumption phase of the study will follow a randomized crossover design in which participants' rate of gastric emptying, efficacy of dietary lipid digestion and absorption, and production of inflammatory cytokines and biomarkers of metabolism will be assessed before and after consuming a high-fat meal (designed to provide 1 g fat/kg body weight) with or without three apples in one sitting. The Chronic Apple Consumption phase of the study will follow a randomized, controlled, parallel-arm design in which participants' (fasting) production of inflammatory cytokines and biomarkers of metabolism, as well as their gut microbiota profile, will be assessed before and after consuming three apples (or no apples) daily for six weeks. We hypothesize that the consumption of three whole apples in one sitting and daily for six weeks will improve these parameters in overweight and obese individuals at risk of developing chronic metabolic diseases.