I think part of the reason that people say that a plant-based diet will make you skinny is because we have an idea in our heads that skinny equals good and healthy. Diets and looking thin are constantly pushed by many forms of media; websites, magazines and tv shows (see Figure 1). There are even some famous celebrities, such as Kelly Osbourne and Alanis Morissette, who have tried a plant-based diet in order to lose weight. It turns out though, that you can be thin and unhealthy, unfit, undernourished and have a terrible personality. Thin does not equal good.
The other reason that people probably say this is because there is evidence to support the idea that switching to and/or maintaining a vegan diet results in weight loss or at the very least, smaller weight gains (Rosell, Appleby, Spencer & Key 2006; Turner-McGrievy, Barnard & Scialli 2007). Research has indicated that vegetarians have a lower BMI than non-vegetarians, as well as a lowered 'risk' of being overweight or obese (Key, Appleby & Rosell 2006; Newby, Tucker & Wolk 2005; Spencer et al 2003; Waldmann et al 2003). It is possible that there are co-factors involved such as less consumption of alcohol and cigarettes (Waldmann et al 2003) or just generally being more health and weight conscious, although so far it seems these may only have a small effect (Spencer et al 2003).
This myth has a few negative side effects. First, it creates an idea that every vegan will be thin, because hey, they're just eating plants and I've been told that a plant-based diet will make me thin. Vegans that don't fit into this mould will be seen as having failed. Some fat vegans have actually been told that they need to lose weight to help the vegan movement. I don't know about you, but I don't want to be part of a movement that is telling people what to do with their bodies; telling them that their bodies are not right and not accepted. That's just wrong. I feel like the vegan movement needs a lot more body acceptance injected into it.
Secondly, this myth encourages people to try a plant-based diet as a weight loss tool. It has no other incentives attached to it so there's no reason for a person to stay eating plants once they have either achieved their goal, or failed. It is possible that this trial will cause them to think more about their relationship with what (or who) they are eating, however.
The third one is pretty important. Well, they all are. There is research that suggests that some people use vegetarian diets as a way to hide their eating disorder and restricted eating habits, and that there is a higher risk of developing an eating disorder amongst vegetarians (Bas, Karabudak & Kiziltan 2005; Klopp, Heiss & Smith 2003; Martins, Pliner & O'Conner 1999). It's possible that the studies had some flaws which influenced the outcomes, as a review of some studies relating to vegetarianism and disordered eating seemed to suggest that it was semi-vegetarianism as opposed to 'true vegetarianism' and veganism that was related to disordered eating (Timko, Hormes & Chubski 2012). I believe, however, that it is best to approach this with caution as approximately 9% of people in Australia are affected by an eating disorder (National Eating Disorders Collaboration 2012).
The link between veganism and vegetarianism and disordered eating may or may not be related to the idea that a plant-based diet will make a person skinny, but by encouraging the idea that people should be skinny and strive to be skinny, and that a plant-based diet will make this so, we encourage people to try and be skinny, rather than accept their bodies, and we make it so that weight loss on a veggie diet is seen as normal, rather than as something for people to be concerned about. Some people have found that becoming vegan has changed their relationship with food and with their bodies in a positive way, but for others this may not be the case.
To sum it all up, yes, a plant-based diet has an increased chance of making you thinner, but it might be related to other healthy lifestyle factors. This myth does hold a small amount of truth, but pushing it can cause damage to the mental health of people who are not skinny (and don't want/need to be) and can encourage the 'skinny is best' culture that is harmful. When telling people this myth, please take these things into consideration.
If you or someone you know is struggling with an eating disorder, I encourage you to contact these following organisations for help and guidance:
The Butterfly Foundation
Support Line: 1800 33 4673 (Monday–Friday 8am to 9pm)
Eating Disorders Victoria
Support Line: 1300 550 236
National Eating Disorders Collaboration
EDIT: Thank you to Margy who commented about how eating disorders are not always motivated by weight loss, but can be about 'food rules', with veganism containing a lot of 'rules' such as no dairy and no meat, which makes it easier for people to avoid eating. For more information on eating disorders, please see the above links.
- Bas, M, Karabudak, E & Kiziltan, G 2005, “Vegetarianism and eating disorders: association between eating attitudes and other psychological factors among Turkish adolescents”, Appetite, vol. 44, no. 3, pp. 309 – 315.
- Key, T, Appleby, P & Rosell, M 2006, “Health effects of vegetarian and vegan diets”, Proceedings of the Nutrition Society, vol. 65, no. 1, pp. 35 – 41.
- Klopp, S, Heiss, C & Smith, H 2003, “Self-reported vegetarianism may be a marker for college women at risk for disordered eating”, Journal of the American Dietetic Association, vol. 103, no. 6, pp. 745 – 747.
- Martins, Y, Pliner, P & O'Conner, R 1999, “Restrained eating among vegetarians: Does a vegetarian eating style mask concerns about weight?”, Appetite, vol. 32, pp. 145 – 154.
- National Eating Disorders Collaboration 2012, “An Integrated Response to Complexity: National Eating Disorders Framework 2012”, National Eating Disorders Collaboration, viewed 23rd October 2013, <http://www.nedc. com.au/files/pdfs/National%20Framework%20An%20integrated%20Response%20to%20Complexity %202012%20-%20Final.pdf>.
- Newby, P, Tucker, K & Wolk, A 2005, “Risk of overweight and obesity among semivegetarian, lactovegetarian and vegan women”, The American Journal of Clinical Nutrition, vol. 81, no. 6, pp. 1267 – 1274.
- Rosell, M, Appleby, P, Spencer, E & Key, T 2006, “Weight gain over 5 years in 21 966, meat-eating, fish-eating, vegetarian and vegan men and women in EPIC-Oxford”, International Journal of Obesity, vol. 30, no 9, pp. 1389 – 1396.
- Spencer, E, Appleby, PN, Davey, GK & Key, TJ 2003, “Diet and body mass index in 38 000 EPIC-Oxford meat-eaters, fish-eaters, vegetarians and vegans”, International Journal of Obesity, vol. 27, no. 6, pp. 728 – 734.
- Timko, C, Hormes, J & Chubski, J 2012, “Will the real vegetarian please stand up? An investigation of dietary restraint and eating disorder symptoms in vegetarians versus non-vegetarians”, Appetite, vol. 58, no. 3, pp. 982 – 990.
- Turner-McGrievy, G, Barnard, N & Scialli, A 2007, “A Two-Year Randomized Weight Loss Trial Comparing a Vegan Diet to a More Moderate Low-Fat Diet”, Obesity, vol. 15, no. 9, pp. 2276 – 2281.
- Waldmann, A, Koschizke JW, Leitzmann, C & Hahn, A 2003, “Dietary intakes and lifestyle factors of a vegan population in Germany: results from the German Vegan Study”, European Journal of Clinical Nutrition, vol. 57, no. 8, pp. 947 – 955.