Diet foods – just how diet are they?

Artificially sweetened drinks and foods have become fashionable over the last decade or two (and not just for their volcanic reaction with Mentos).

Recommended by nutritionists to combat the growing effects of global obesity, they are the low-calorie alternatives to sugary soft drinks, sodas and sweets. Juices, confectionery and ice-creams are all offering low calorie alternatives sweetened with these compounds.

But how effective are they in reducing weight gain or promoting weight loss? On the surface, they seem very effective. Studies on rats [1] and people [3] have shown replacing sugary foods and drinks with the diet alternatives prevents, and can be used to treat, obesity. But not all studies are this rosy.

Diet foods/drinks may be able to fool the brain into thinking sweet foods contain less calories than they actually do. This could lead to over-indulgence of other foods as the brain loses the ability to correctly calculate the calorific intake of sweet foods (whether artificially or sugar sweetened).

A study on humans [2] showed that people who drank a sugared drink after exercise, reduced the calorie intake at a subsequent meal by the total amount of calories contained in the sugary drink. This showed that the brain is normally aware and can accurately calculate the calories regularly consumed. Those people given an artificially sweetened drink did not reduce consumption at a later meal – also implying that the brain was aware of the low-calorie nature of the fluid.

However, if people regularly consume low calorie sweets, this calorie calculation can be affected. A study using rats [4] demonstrated that those used to the “empty” calories of artificially sweetened drinks would consume more calories when given a sugary substitute than those who regularly consumed sugar – presumably because the brain had “re-calibrated” the calorie content of sweet foods.

Regularly consuming artificially-sweetened foods and drinks could therefore increase the consumption of calories on binge eating sessions by making the brain under-estimate the calorific load.

Thus consuming diet foods may not be (entirely) the calorie-saving option you’d hoped. It seems that the old advice about reducing the consumption of sweet foods and drinks and increasing exercise may be the only sure-fire way to diet.

But don’t fear, whatever their effect on your hips, they can be light on your pocket. Diet drinks can turn anyone into a cheap drunk. A recent study shows that drinks made with diet mixers are absorbed faster and thus the drinker will become drunker faster[5].


[1] Porikos KP, Koopmans HS (1988) The effect of non-nutritive sweeteners on body weight in rats. Appetite 11 Suppl 1: 12-15
[2] King NA, Appleton K, Rogers PJ, Blundell JE (1999) Effects of sweetness and energy in drinks on food intake following exercise. Physiol Behav 66: 375-379
[3] St-Onge MP, Heymsfield SB (2003) Usefulness of artificial sweeteners for body weight control. Nutr Rev 61: 219-221

[4] Davidson TL, Swithers SE (2004) A Pavlovian approach to the problem of obesity. Int J Obes Relat Metab Disord 28: 933-935
[5] Wu KL, Chaikomin R, Doran S, Jones KL, Horowitz M, Rayner CK (2006) Artificially sweetened versus regular mixers increase gastric emptying and alcohol absorption. Am J Med 119: 802-804



Filed under Curious Science, Household Science, Science

2 responses to “Diet foods – just how diet are they?

  1. Hi,
    I've had several friends mention that they lost weight during their recovery period. What is the average amount of weight most women lose? I can

    understand a few pounds for not wanting to eat, but some friends mentioned more like 15lbs. Is this true?

  2. Hi Kristopher,

    What were they recovering from?

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