Do I get hungry on a liquid-only plan?
Solid or liquid...nutrition is a personal decision.
We'd usually try to focus on a liquid only strategy for long distance racing due to its simplicity in carrying what you need. However, often we get asked "what happens if I get hungry?!" as people 'need' solids.
It’s perfectly acceptable to use solid foods too (especially if you need that full-feeling in the stomach) but they take longer to digest and you still need to take on fluids to stay hydrated. However, you may find that your digestive system handles gels better than solids, or vice versa. It may not even bother you that much at all and you can transition onto solid foods easily. If you're training for an endurance event, it's important to test different liquids and foods during your long training runs so you can know what works best for you. You don't want to try anything new on race day. It is important to note that if the you are consuming a high volume of fluids with adequate energy in them, then you will feel like you have eaten a lot as there is still a high amount of substance there. Think about how full you feel if you have a pub session drinking just beers – you get quite full!
However, take note of what works best for you...trialling all different options of course!
The other factor to consider is convenience based on the event and duration. If you're doing a race, you can always get sports drinks or water from the aid stations (as long as they have the product that you like and have trained with). But if you rely on just sports drinks during your long training runs, you may have to stop to get more along the way. If you use food, you'll most likely be able to carry enough fuel for your entire run in your pockets or running belt, but you will also need to hydrate as well, which adds weight to carry.
Studies have shown that solid fuel was equally as effective, over a 3 hour aerobic cycling session, as liquid / gel fuel (1)(2)(3)(4)(5) in absorbing the fuel required. However, similar studies undertaken, using triathletes, showed that once running is introduced, the liquid/gel fuel performance far surpassed the solid fuel nutrition, due to the jarring and sloshing motions exerted on the body when running.
References
(1) Lamb, Synder, et al.1991;
Lamb, D.R., Snyder, A.C., Baur, T.S. (1991). Muscle glycogen loading with a liquid carbohydrate supplement. International Journal of Sport Nutrition 1, 52–60.
(2) Coleman 1994;
Coleman, E. (1994). Update on carbohydrate: Solid versus liquid. International Journal of Sport Nutrition 4, 80–88.
(3) Mason et al. 1993;
Mason, W.L., McConell, G., Hargreaves, M. (1993). Carbohydrate ingestion during exercise: Liquid vs solid feedings. Medicine and Science in Sports and Exercise 15, 966–69.
(4) Lugo et al. 1993;
Lugo, M., Sherman, W.M., Wimer, G.S., Garleb, K. (1993). Metabolic responses when different forms of carbohydrate energy are consumed during cycling. International Journal of Sport Nutrition 3, 398–407.
(5) Robergs et al. 1998;
Robergs, R.A., McMinn, S.B., Mermier, C., Leadbetter, G., Ruby, B., Quinn, C. (1998). Blood glucose and glucoregulatory hormone responses to solid and liquid carbohydrate ingestion during exercise. International Journal of Sport Nutrition 8, 70–83.