Recently there has been much discussion around proposed legislation to mandate restaurants to prominently display energy values (calories) on their menus. The premise is that consumers will easily be able to identify foods with lower calories and make healthier choices. Obviously, this is a reactionary response to the obesity epidemic. Although, I am in support of labeling to better inform consumers and encourage healthy choices, I worry that focusing only on calories may have unintended, negative side effects.
In order for restaurants to maintain profits, it seems logical that they would reduce the caloric content of some of their items. In some cases, the response has been to reduce portion sizes, an excellent strategy from a scientific perspective but perhaps not one that will appeal to the consumer. The second strategy, is to reduce the energy value of foods by using low calorie sugar and fat substitutions. This strategy is already prevalent in processed food products (sodas, chips, crackers, sauces etc). Intuitively, this strategy makes sense; fewer calories should equal weight loss. Unfortunately, research does not seem to support the link between fat and sugar replacers and a healthy body weight.
Terry Davidson’s group at Purdue University has done a significant amount of work regarding the effects of sugar and fat replacers on body weight. Their results have lead them to theorize that foods that mimic the texture, taste, etc. of fats and sugars without providing the expected calories, affect the body’s energy balance, promoting weight gain (1). For example, a sweet tasting food signals to the body that calories are coming and induces a series of physiological responses in preparation.
When the calories don’t come as expected, the body becomes confused. The relationship between sweet taste and food is affected. Then when you eat something sweet and high in calories, the body isn’t expecting the calories and doesn’t deal with them as well. This can lead to weight gain. Indeed they report increased body weight and body fat with artificial sweeteners as compared to glucose due to reduced caloric compensation (the body’s natural response to self-regulate total energy intakes) (2).
Caloric compensation was also reduced with a low-fat Olestra (fat replacer) potato chip (3). In an article published this month, in Behavioral Neuroscience, they studied the long-term effects of the low-fat Olestra potato chip on rats fed a high fat diet. They report that rats exposed to a low-fat Olestra potato chip, consumed more calories and gained more weight than those rats exposed to the high-fat chips, when the rats ate a high fat diet. Interestingly, there was no effect of the Olestra chips when the rats were on a normal (not high fat) diet. They also found that the effects lasted even when the rats were no longer eating the low-fat chips (4). In short, the low calorie sugar and fat replacers reduce the body’s ability to deal with real sugar and fat causing weight gain.
This research provides a possible theory as to why several studies find non-caloric sweeteners increase obesity and associate co-morbidities (5,6) and suggests fat replacers are likely to have the same effects. The current trend of focusing on a particular nutrient (calories, fat etc.) is not likely to lead to improvements in body weight. Furthermore, if food companies respond to the pressure to reduce the caloric content of their foods by using fat and sugar substitutes rather than healthier ingredients and smaller portion sizes, they may exacerbate the obesity epidemic rather than curb it.
(1) Davidson TL, Swithers SE. A Pavlovian approach to the problem of obesity. Int J Obes Relat Metab Disord 2004 Jul;28(7):933-935.
(2) Swithers SE, Martin AA, Davidson TL. High-intensity sweeteners and energy balance. Physiol Behav 2010 Apr 26;100(1):55-62.
(3) Swithers SE, Doerflinger A, Davidson TL. Consistent relationships between sensory properties of savory snack foods and calories influence food intake in rats. Int J Obes (Lond) 2006 Nov;30(11):1685-1692.
(4) Swithers SE, Ogden SB, Davidson TL. Fat substitutes promote weight gain in rats consuming high-fat diets. Behav Neurosci 2011 Aug;125(4):512-518.
(5) Lutsey PL, Steffen LM, Stevens J. Dietary intake and the development of the metabolic syndrome: the Atherosclerosis Risk in Communities study. Circulation 2008 Feb 12;117(6):754-761.
(6) Fowler SP, Williams K, Resendez RG, Hunt KJ, Hazuda HP, Stern MP. Fueling the obesity epidemic? Artificially sweetened beverage use and long-term weight gain. Obesity (Silver Spring) 2008 Aug;16(8):1894-1900.