This becomes pervasive in the social movements I navigate, because people in those movements have defined restrictive dieting--and even moderation dieting, in some cases--as a form of oppression. With the exception of religious/ethical restrictions and so-called "legitimate" medical reasons, dieting is portrayed as the product of sexist and body-shaming imagery in the media rather than a personal choice.
Although it's important to analyze those images (including in diet-related imagery), we need to realize that dieting and food restriction is an individual choice for which people might have many different reasons:
- Religious Restrictions (kosher, halal, Hindu dietary restrictions, fasting)
- Cultural Reasons (in America we don't usually eat dogs)
- Health Philosophy (any long-term diet meant to create optimal health)
- Ethical Philosophy (vegan, fruitarian, vegetarian)
- Body Dysphoria ("lose muscle, gain fat!" for trans women, for example)
- Personal Preference (sometimes you just don't like certain things)
- Food Addiction (elimination of trigger foods to prevent binge eating)
- Political Philosophy (conscious consumerism, decolonizing diets)
- Allergies and Intolerances (elimination of foods that make you feel terrible, regardless of diagnosis)
- Management of Specific Health Challenges (diets meant to manage diabetes, Crohn's, celiac, autism, etc.)
- Control Issues (the ability to select foods makes a person feel more in control of themselves)
One of the places I get this most is in the fat positive/body positive movement. In this movement, dieting tends to be socially frowned upon because of the association of someone's personal dietary decisions with dietary evangelism or body shaming imagery used to promote diets and the diet industry. Criticism of this industry and evangelism in general is necessary, but where this attitude fails is in making the exact same body shaming arguments fatphobic people make to denigrate other peoples' preferred body compositions and eating habits.
In other words, there is nothing "body positive" about policing other peoples' feelings about their bodies.
To tie in to part 1, all of this has to do with our culturally and personally defined perspective on "real food" as well as our largely arbitrary standards of beauty. The idea that ridiculously skinny is an appropriate standard of beauty is oppressive and shames fat people... but making this point at the expense of people who are unsatisfied with their body composition is not body positive and dissolves our right to make that call ourselves.
As a trans man this also hits me because the "love your body whatever it is" line is one that is implied in cissexist arguments. My journey to manhood has been mourned by some as a response to my inability to adhere to unrealistic standards of beauty. In the same way, my desire to change my body composition (which is in large part due to my gender dysphoria, incidentally) is painted as an oppressive response to the way I feel about my body that should be shamed out of me rather than left to my personal devices.
The main conclusion? We need to, as a whole, trust that we are not the ones who know what's right for others as far as their individual dietary decisions, even if they are restricting in ways we are not comfortable with.
* -- Addition: Sometimes people will throw around discussion of legitimate eating disorders when this topic comes up. The main issue with this is that most restrictive eating habits do not actually fit the definition of a medically-recognized eating disorder, so calling them such is hyperbole. Aside from this, I personally adhere to a risk-aware/harm-reduction philosophy; although I maintain most restrictive eating is not a medically classifiable eating disorder, all have risks that people need to be aware of and ways of making those habits safer. Focusing on these is, I feel, preferable to making people with either restrictive diets or eating disorders unwilling poster children for body image campaigns or shaming people who eat different.