Ironically, I’d like to start this post with a short video: Louis C.K. – Eating Habits.

Pizza, ice cream, and chocolate – we’ve all had days where we can’t resist gorging on calorie-dense foods. Maybe you had an uncontrollable urge, a stressful day, lacked the motivation to work-out. However, have you ever considered how your physical activity levels affect your eating habits?

Nutrition is a somewhat multifaceted science. The effects of nutrition are many, influencing variables such as immunity, metabolic function, athletic performance, etc. Thus, with the constant emergence of novel research opinions can be rather fluid e.g. a reduction in saturated fatty acid (SFA) intake has been central to many dietary recommendations to reduce the risk of cardiovascular disease (CVD). However, emerging epidemiological evidence suggests that there is an inverse association between high milk consumption and incidence of CVD; which can obviously obscure the definition of healthy eating. Regardless, the World Health Organisation (WHO) defines a healthy diet as achieving energy balance, limiting energy intake from total fats, free sugars and salt and increasing consumption of fruits and vegetables, legumes, whole grains and nuts (McGill et al. 2015).

In accordance with this definition, a clear trend for greater time spent performing sedentary activities has been shown to be associated with unhealthy eating – exhibited by less fruit and vegetable consumption, lower scores on the healthy eating index (HEI), and higher levels of consumption of energy dense foods, such as high-fat foods, sugary snacks, soft drinks and fast food (Hobbs et al. 2014, Lee et al 2013).

This trend is fairly consistent among current literature with findings indicating that changes in television and computer/game use are associated with unhealthy eating behaviours; television use and leisure-time physical activity exhibiting an inverse association; and, television use indicating a positive association with the consumption of sweets and soft drinks and an inverse relationship with the consumption of vegetables (Pearson et al. 2014, Gabremariam et al. 2013).

The primary culprit for this trend is presumed to be the advertisement industry, resulting in the repeated exposure of snack foods and other energy-dense, nutritionally poor food sources, subsequently guiding the replacement of less advertised foods such as fruits and vegetables (Anderson et al. 2006). However, not to discredit the impact of advertising, sedentary behaviour may also influence eating habits via the ‘displacement hypothesis,’ whereby one behaviour (e.g. sitting) displaces another (e.g. physical activity)(Pearson et al. 2014).

As people who perform less physical activity often eat less healthy foods an undocumented belief exists that there is a relationship between the decision to participate in physical activity and the decision to eat a healthy diet, and, although research on this topic is ongoing, some interesting observations exist…

Various studies provide evidence that healthy nutrition and physical activity are positively related to each other with both health behaviours appearing to rather facilitate than hinder each other. This has been indicated by such findings as a significant positive correlation between physical activity and healthy snacks. Interestingly, similar to eating patterns associated with sedentary behaviour possible implicit variables linking physical exercise and nutrition may include peer pressure, cultural values, advertising, fashion or risk aversion (Tavares 2014). However, the role of cognition appears to be of substantial importance.

Research has shown that certain risk behaviours occur in combination and tend to cluster within individuals. Coincidentally, it has been suggested that individuals who believe that they are able to engage in physical activity despite barriers hold more positive beliefs about their ability to change their nutrition. Similarly, individuals who are motivated to change their physical activity levels have been found to also hold the intention to change their nutrition, expressing a positive association with the intention to consume fruit and vegetables (Fleig et al. 2015). This relationship between physical activity and healthy nutrition may be somewhat dominated by confidence: key to successful cross-behaviour regulation is the availability of self-regulatory resource (according to the self-control strength model efforts in one domain can have implications for regulating other domains); with increasing habit strength (the degree to which a behaviour has acquired features of a habit), the pool of available self-regulatory resources rises as behaviour enactment becomes more efficient; if individuals follow an exercise routine rather effortlessly, self-regulatory resources occupied by exercise-specific demands become vacant and can be invested in other behaviour tasks such as planning one’s diet (Fleig at al. 2014). Essentially, with increased confidence the ability to perform physical activity becomes less taxing, benefiting self-efficacy and the potential of cognitive transfer to engage in healthy nutrition, assisting self-regulatory strategies (i.e. planning) and intention.

Although research regarding a positive activity-nutrition association is ongoing, many causes of morbidity and premature mortality are influenced by multiple health risk behaviours including physical inactivity and unhealthy nutrition, thus the manipulation of this suggested positive relationship could be plenty useful. In particular, policy implications could be of considerable importance. For instance, the consideration that simultaneous changers may maintain an advantage as they experience synergistic effects when changing related behaviours and are more confident about their ability to regulate multiple goals (Fleig et al. 2015) could imply that combining physical education with food education may be a worthwhile consideration. Therefore, as mentioned in my first post (The Jamie Oliver Effect), the utilisation of connectedness to nature via exposure to garden-based nutrition programs – with exposure to gardens showing a positive association with physical activity – may be notably beneficial in promoting positive health behaviours.

Maybe “you cannot outrun a bad diet” but maybe you could run yourself into a healthy diet.