Fast foods, energy density and obesity: a possible mechanistic link

Abstract

Fast foods are frequently linked to the epidemic of obesity, but there has been very little scientific appraisal of a possible causal role. Here we review a series of studies demonstrating that the energy density of foods is a key determinant of energy intake. These studies show that humans have a weak innate ability to recognise foods with a high energy density and to appropriately down-regulate the bulk of food eaten in order to maintain energy balance. This induces so called 'passive over-consumption'. Composition data from leading fast food company websites are then used to illustrate that most fast foods have an extremely high energy density. At some typical outlets the average energy density of the entire menus is approximately 1100 kJ 100 g(-1). This is 65% higher than the average British diet (approximately 670 kJ 100 g(-1)) and more than twice the energy density of recommended healthy diets (approximately 525 kJ 100 g(-1)). It is 145% higher than traditional African diets (approximately 450 kJ 100 g(-1)) that probably represent the levels against which human weight regulatory mechanisms have evolved. We conclude that the high energy densities of many fast foods challenge human appetite control systems with conditions for which they were never designed. Among regular consumers they are likely to result in the accidental consumption of excess energy and hence to promote weight gain and obesity.

Fast food: unfriendly and unhealthy

“…3 Energy density In addition to large portion sizes, fast food is also characterised by high-energy density, that is high energycontent/food-weight ratio. The energy density of the entire menu at fast-food outlets is typically B1100 kJ/100 g. 4 This is 65% higher than the average British diet (B670 kJ/100 g) and more than twice the energy density of recommended healthy diets (B525 kJ/100 g). Humans have only a weak innate ability to recognise foods with high-energy density and to downregulate the bulk eaten to meet energy requirements appropriately.…”

“…Humans have only a weak innate ability to recognise foods with high-energy density and to downregulate the bulk eaten to meet energy requirements appropriately. 4 Industrially produced trans fat French fries and fried meat from fast-food outlets contain high amounts of industrially produced trans-fatty acids. Trans fats are fats in margarines, spreads, and frying oils, produced by industrial hardening of vegetable or marine oils, to make the product more stable and robust for handling and storage.…”

Brain neuropeptide Y and CCK and peripheral adipokine receptors: temporal response in obesity induced by palatable diet

“…2 Physiological experiments illustrate that energy-dense diets can potentially compromise normal appetite regulation in humans. 3 This study aimed to specifically explore the impact of palatable foods on appetite and metabolic regulation.…”

Fast-food consumers in Singapore: demographic profile, diet quality and weight status

“…'Western' fast food tends to be energy-dense, nutrientpoor items which can undermine appetite regulation and may lead to 'passive over-consumption' (8) . Fast-food consumption has been associated with poorer diet quality, such as lower wholegrain intake (9) , lower fruit intake (9)(10)(11) , lower vegetable intake (9,10,12) and higher intakes of fat and saturated fat (10) .…”