Feeling unusually hungry after a swim…

Question:
I often feel unusually ravenous after swim training. Is there a physiological reason for this, and if so, how can I manage it?

Answer:
Some recent research at Loughborough measured the appetite hormone ghrelin, and found that during swimming, ghrelin levels and appetite was actually suppressed, which is often the case with prolonged or intense exercise. However in the hours after swimming, ghrelin, and hence appetite, did increase, although this didn’t result in swimmers necessarily eating more than the control group. This research is well contrasted with investigation by the same group of researchers, looking at the appetite-stimulating effects of 60 minutes of moderately brisk walking. Results demonstrated that, despite inducing a moderate calorie deficit, a bout of brisk walking did not lead to an increase in appetite, the hormone ghrelin, or in energy intake. More research is clearly needed, but it appears that swimming may indeed stimulate appetite after exercise. Although the physiological basis for this is not fully understood, past research indicates it may be linked to temperature of the water. A study published in the International Journal of Sports Nutrition and Exercise Metabolism back in 2005 demonstrated that cold water stimulated post-exercise energy intake. Subjects exercised for 45 minutes on a submersed cycle ergometer in cold water, neutral water, or rested for 45 minutes. They found that exercising in cold water (20 degrees) stimulated post-exercise energy intake significantly more than the other conditions. Unfortunately, the study design here is very different, and since the type of exercise is not remotely similar to swimming, no real comparisons can be made to the other research studies. I would say that if you do find swimming stimulates your appetite more than usual, try making sure you take a protein-rich snack soon after your swim. Protein helps to suppress hunger, and effectively balances blood sugar levels. Consider timing of eating pre and post swimming, ensuring that your blood sugar levels are not too low prior to a swim, and that you replenish energy soon afterwards. Firstly, avoid sugary cereals before a swim, which will simply drive hunger, and likely send your blood sugar levels crashing! Choose a suitable protein-rich snack to have after your swim, e.g. plain yogurt with added seeds and some fresh fruit, or scrambled eggs with toasted rye bread, or a yogurt-based fruit smoothie, or a fish, chicken, or egg-based salad.

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