Solid food found to be more satisfying

Here in the UK, temperatures have dropped noticeably of late, which naturally leads people to seek out warmer, ‘heartier’ food than, say, summer salads. One option here is to eat a bog-standard ‘primal meal made up of meat, fish or eggs (e.g. omelette) with some vegetables. Such options are ‘doable’ for most in the evening, but at lunchtime may not be convenient. Not everyone has the time or facilities to be able to make or buy and eat such a meal. So what to do?

One option might be to eat soup. Here in the UK, most sandwich shops offer soups, usually at least two varieties. The norm is for there to be at least one vegetarian and one non-vegetarian soups to be on offer. For non-vegetarian folk, I generally recommend the ‘meaty’ soup if it’s available. One reason for this is that such a soup will generally be more filling and satisfying than a vegetarian soup.

The reality is that most individuals will get more out of eating beef and black bean or chicken broth than eating carrot and coriander or tomato and basic soup. I am not of the mind that lunch needs to last all the way to an evening meal perhaps 8 hours later. However, for many, eating a vegetarian soup will leave them hungry a couple of hours later. One with meat, fish or seafood in tends to last twice much longer.

One reason for this may have to do with the fact that non-vegetarian soups tend to be richer in protein, which does tend to fill a hole more effectively than, say carbohydrate. Another reason might have to with the fact that non-vegetarian soups may require a bit of chewing. Chewing food and having it spend some time in the mouth prior to swallowing does tend to enhance the satisfaction derived from that food. The other side of this coin is that many vegetarian soups (see example above) are quite blended in texture and can therefore be ‘drunk’ rather than eaten.

The relevance of these factors came home to me recently on reading a study which assessed the effects of solid and liquid meals on hunger suppression [1]. In this study, individuals were fed high protein meals matched for calorie content and make-up, but differed in terms of their form: on one occasion, the participants were fed the meal in solid form, while on another occasion, the meal was fed to them in liquidised form.

About two hours after eating, individuals had less desire to eat and more ‘hunger suppression’ after eating the solid meal compared to when they had eaten that meal in liquid form. This finding appears to provide at least some evidence for the idea that eating something ‘solid’ may have the ability to keep us satisfied for longer. This finding is in keeping with several other studies that have found the same thing.

In this particular study, ‘oral processing time’ was the essentially the same for both meal forms. This means that it was unlikely the improved satisfaction derived from the solid meal was related to increased chewing.

Another mechanism which may influence satisfaction relates to the secretion of certain hormones such as insulin and ghrelin which tend to stimulate appetite. Previous studies have suggested that solid meals can lower the levels of these hormones compared to liquid meals. However, in the study reported here, there was not difference in the levels of these hormones between different meal forms.

We may not have all the answers regarding the why solid food tends to be more satisfying, but this fact should perhaps stimulate us to think about emphasising more solid fare in our diets. One option here might be, in the winter, to opt for dishes such as stews and casseroles. As it happens, on Sunday I cooked a beef stew which I’ve eaten twice since (Sunday night and Monday night). On both occasions, a small bowl has really ‘hit the spot’. Would the effect have been the same if I’d blended the stew into a smooth soup? I don’t know. My sense is not.

References:

1. Martens MJ, et al. A solid high-protein meal evokes stronger hunger suppression than a liquified high-protein meal. Obesity (Silver Spring) 21 october 2010 [epub ahead of print]