The current food environment in most Western cultures is far removed from the environment in which our hunter-gather ancestors lived. Our supermarket shelves are stacked with countless variations of highly processed foods which has sparked a lively debate regarding the merits of food processing and the extent to which it might influence overconsumption and weight gain. Our lab group has focused its research in this area on four main topics: responses to the energy content and macronutrient composition of foods, the relationship between sugar and appetite, and the role of low-calorie sweeteners in our diet.  

Energy density and macronutrient composition 

Energy density (kcal/g) is the amount of energy, or calories (kcal), per unit weight of food (usually grams, g). A higher energy density means that there are more calories per gram of that food. For example, cucumbers have an energy density of 0.14 kcal/g whereas fries from a fast-food restaurant are approximately 3.2 kcal/g. Historically, our diet rarely exceeded 1.75 kcal per gram, which may make us poorly adapted to modern foods. Research in our lab has supported this idea of ‘evolutionary discordance’ and our findings suggests that humans undervalue foods with an ‘unusually high’ energy density(Brunstrom, Drake, Forde, & Rogers, 2018).  

Annika Flynn (Ph.D student, supervised by Jeff Brunstrom), has taken this further and is looking at how energy density influences the amount of food that we select and consume. In collaboration with Professor Kevin Hall, we have been comparing low and high energy-dense foods. With low energy-dense foods, people tend to consume meals that are the same volume, whereas with high energy-dense foods they show surprising sensitivity to calorie content, (indeed they even overcompensate – people consume fewer calories from meals that especially energy rich), which might reflect an important underlying ‘calorie sensing’ mechanism. Together, this work helps to inform our understanding of humans engage with modern foods, and how they influence energy balance over time.  

Some researchers also highlight recent changes in the macronutrient composition of the foods that we eat (DiFeliceantonio et al., 2018).One idea is that foods that are high in fat and carbohydrate are historically unusualand this makes them especially rewarding. Building on this, Annika Flynn has been studying how combinations of macronutrients influence dietary behaviour and food choice (also section headed ‘Protein and sustainability’). Her work has focused on food choice in multi-component meals, where more than one food item is selected and consumed.  

Example publications: 

• Brunstrom, J. M., Drake, A. C. L., Forde, C. G., & Rogers, P. J. (2018). Undervalued and ignored: Are humans poorly adapted to energy-dense foods? Appetite, 120, 589-595. Appetite, 120, 589-595.  

It is clear, nonetheless, that high sugar intake is likely to contribute to weight gain. The same is true for other dietary choices which contribute to increased energy density of our diet. 

Low-calorie sweeteners 

Low-calorie sweeteners such as saccharin, aspartame, sucralose and stevia provide sweet taste with very few or zero calories. Therefore, when consumed in place of sugar, low-calorie sweeteners can be expected to reduce overall calorie intake and help with weight control. Concern, however, has been raised that they might have the opposite effect, although often research findings are cited selectively (‘cherry-picked’) to support one view or another (Mela et al., 2020). In response to this and the resulting uncertainty that prevails about the usefulness of low-calorie sweeteners for weight management, we carried out a systematic review of relevant evidence from studies in animals as well as humans (Rogers et al., 2015). We recently updated this review (Rogers & Appleton, 2021), where we also included studies investigating effects of low-calorie sweeteners administered in capsules versus placebo capsules.  

The weight of evidence is clearly in favour of low-calorie sweeteners consumption. Specifically, our reviews found that a variety of randomised, controlled intervention trials demonstrate that low-calorie sweeteners versus sugar consumption reduces energy intake and body weight. These types of studies provide the strongest form of evidence – superior to animal and observational studies. Overall, this evidence is consistent with the lack of full compensation for short term (meal to meal) increases or decreases in energy intake. Furthermore, it refutes claims concerning adverse effects of low-calorie sweeteners caused by increased preference for sweetness, or through confusing the relationship between sweetness and energy intake (Rogers, 2018).   

Example publications: