The Effects of Exercise on Taste and Food Preference

There are five basic tastes: sweet, sour, salty, bitter and umami (Brown, 2015). Sweetness is perceived in foods containing sugars such as sucrose, fructose and glucose (Institute for Quality and Efficiency in Health Care [IQWIG], 2016). The salty taste perceived in foods is due to the salt crystals made of sodium and chloride (NaCl) (IQWIG, 2016). Bitter taste comes from different compounds including caffeine, theobromine found in chocolate and phenolic compounds (Brown, 2015). Sourness is perceived in foods containing acids (Brown, 2015) Umami taste is caused by glutamic acid or aspartic acid and it results in a meaty taste (IQWIG, 2016). The taste of food depends on the chemical and physical properties of the food which are characterized by taste, aroma and texture, but the taste also depends on the physiological and psychological state of the person who is eating the food (Narukawa et al., 2010). Physical activity causes physiological changes in the body influencing the palatability of food which is defined as the hedonic value (pleasant or unpleasant) of food (Narukawa et al., 2010 and Elder & Roberts, 2007). Therefore, after exercise it is possible that the taste and the preference for certain foods change. During exercise, sweet-tasting foods containing glucose provides the energy required by the body to do the physical work (Narukawa et al., 2010). Thus, does physical activity affect sweet taste sensitivity and preference? Before answering this question, a description of the literature will be done to see what is known on the effects of exercise on sweet taste sensitivity and then the mechanism of action based on concepts from the literature will be explained. A critique of the literature will follow to then decide if the reviewed studies are valid and accurate. Finally, the question will be answered.

The studies selected for the review of the literature had to test the effect of exercise on sweet taste sensitivity and/or sweet food preference. Most studies selected looked at the effects of exercise on the five tastes, but only the results for sweet will be reviewed in this paper.

Nakagawa et al. (1996) reported no significant differences in sweetness perception in subjects with a mean age of 26 years old who exercised on a 100w ergometer for 10 minutes at 60 revolutions per minute (r.p.m).

Westerterp-Plantenga et al. (1997) found that after 2 hours of cycling at 60% of maximal workload (Wmax), perception of sweetness at low concentration increased significantly in healthy untrained obese or non-obese men aged 19-35 years old compared to resting condition. In addition, the preference for energy coming from carbohydrates increased significantly after exercise in comparison to the controls (Westerterp-Plantenga et al., 1997).  

Horio & Kawamura (1998) reported an increase preference for sucrose solutions among students aged 19 to 21 years old after 30 minutes of exercise at an intensity based on the percentage of heart rate during maximal exercise.

Horio (2004) determined the effect of exercise on taste preference for different sweet solutions among healthy students aged 19 to 21 years old. Horio (2004) reported that the preference for sucrose, glucose, steviode, D-sorbitol and erythritol increased after 30 minutes of exercise on a bicycle ergometer at 50% maximum volume of oxygen (VO2max). However, preference for saccharin did not change after exercise (Horio, 2004). Therefore, Horio (2004) concluded that, after physical activity, taste preference for various sweet solutions is increased.

Narukawa et al. (2010) investigated the effect of prolonged exercise inducing physical fatigue on sweet taste sensitivity and palatability in subjects with a mean age of 30 years old who did a hike of 36 km in 12 hours. Two solutions were used for sensory evaluation tests: one 100mM sucrose solution and one 300mM sucrose solution (Narukawa et al., 2010). Towards the end of the hike where the physical fatigue was at its highest, the palatability of the 300mM sucrose solution increased in comparison with the 100mM meaning that the subjects preferred the sweetest solution (Narukawa et al., 2010).

According to the literature, blood glucose decreases during physical exercise because glucose is used to produce energy in the form of ATP (Horio, 2004 & Narukawa et al., 2010). In fact, blood glucose is used in cellular respiration, which includes many pathways, such as glycolysis, Krebs cycle and the electron transport chain, to ultimately produce ATP. In addition to free blood glucose, glycogen from muscles is an important energy source during exercise because glycogen is broken down into glucose molecules which serve as fuel for cellular respiration to produce ATP. Consequently, after exercise glycogen stores and blood glucose are lower which may increase sensitivity to sweet taste and also increase sensitivity to carbohydrates (Horio, 2004 & Narukawa et al., 2010).

Due to the depletion of glucose and glycogen stores, the palatability for sweet-tasting foods containing glucose is higher after physical exercise (Narukawa et al., 2010). The increase in palatability can be explained by the theory of physiological usefulness stipulating that any food of physiological usefulness in a particular physiological situation will be perceived as pleasant (Appleton, 2005). We can apply this theory to explain the higher palatability for sweet-tasting foods after exercise. In a physiological situation of glucose requirement, the intake of sweet foods containing glucose will be perceived as pleasant by the consumer (Appleton, 2005). Therefore, after exercise, the preference for sweet foods will increase because they are perceived as pleasant since they are needed by the body.

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