When I have encountered such statements from strangers, I've tended to feel judgemental and/or threatened, and sometimes I have acted publicly on those feelings. I've said or supported other people's assertions "If you're losing weight, you aren't part of the fat-acceptance movement." But I had a more, um, compassionate? inclusive? reaction to her statement. I gave some thought to whether I was making an exception for her or whether my thinking had shifted in general. I think it's some of both. I wrote the following comment (edited slightly).
The first time I encountered the fat acceptance movement was when I came across Shadow on a Tightrope. I read essays by women who said they weighed over 300 pounds. I had two responses to this book. I felt glad that someone was finally saying that it was OK to be fat and that fat people should be treated as human beings. Also, I went on the only major diet I've ever been on in my life. (When I got to my lowest adult weight, I felt pretty sick and undernourished. But I was still overweight according to BMI.)
You and I are not the only people who have combined fat acceptance and losing weight. So did Paul Campos, the author of The Obesity Myth. So did Susan Bordo, the author of Unbearable Weight, one of the first books to compare the language of fat-hatred with the language used to describe Jews in Nazi Germany. (She also stated that she felt bad about herself for making that personal choice.)
If accepting your body -- fat or not -- is a requirement for being a proper feminist, then there are very few proper feminists, because most women (and some men) frequently feel unhappy about their bodies, and one of the most common reasons is feeling that your body is too fat.
I prefer to think that feminism is the radical notion that women are people, and that the actions which show someone to be a feminist are actions that support women. Since women are unfairly judged by our appearance (including our weight), publicly stating that fat prejudice is wrong is a good feminist action. It's also a feminist principle that what you do with your body is your own business.
People who can successfully lose weight over the long term are rare, but they do exist. If you are one of them and feel better with a smaller body, then I think you are fortunate in this, and I don't see harm being done. I would like to have a smaller body too. But that seems incompatible with my sanity and other health needs, so I need to focus on health goals other than weight loss ("Health at Every Size" http://en.wikipedia.org/wiki/Health_at_Every_Size ).
Unfortunately there isn't any way to change your weight without other people having opinions about it and likely expressing those opinions publicly. But that's part of society's mistreatment of women. Women's bodies are considered public property and that means people think they get to make assumptions about what the size of your body means and what it means when your body changes size.
What I'm writing here is somewhat different from other things I've said in my LiveJournal. For much of my life post-fat-acceptance I felt personally threatened by people who lost weight. That's not rational because people's personal choices aren't about me.
I do think it's rational for me to be concerned that the vast majority of people who want to change their weight want to lose weight rather than gain weight. I think that shows evidence of social pressure. But that's a problem with society, not individuals.
Also in the past I've said stuff like, "OK, if you lose weight, fine, but don't talk about it in public at all." I still think I would *prefer* if people didn't talk about it -- especially as a casual female-bonding type conversation topic -- but I suspect I'm one or two sigmas over at the "reserved" end of the bell curve about certain personal stuff, and a lot of other people have different ways of handling what to share and what not to share.
I do feel angry/betrayed when someone who is a leader in the fat acceptance movement or is a celebrity who has publicly declared "I'm OK with being fat" then decides to lose weight -- and to be even more public about losing weight than they were about their fat-acceptance.
The following was not part of the comment I posted.
I still really value the idea of spaces (virtual or meatspace) where there is no promotion of weight loss. (Promotion = talking about weight loss as a good thing or a necessary thing in some circumstances.) I feel like those spaces are harder to find than they used to be, and I am very sad about that. For example, I thought I could rely on there not being weight loss promotion at a NAAFA convention, but I was wrong—it came up in multiple panels I attended, and there were events I had to stay away from because I knew they would include such messages. I have also stayed away from NOLOSE in part because I've heard there's some weight loss promotion there.
Lately I am wondering if WLP-free spaces maybe never really existed (except as understandings that develop among specific people who hang out socially) and I am actually mourning my belief in them.
Whether or not they exist (any more) I need to remind myself that there are a lot of places I can go to hang out with fat people, and with people who think fat people are hot, and with people who think prejudice against fat people is wrong. There are a lot more people and places like that in my life than there once were, and that's good for me.