It’s a compliment that rolls easily off the tongue: “You look great…You’ve lost weight!” While some people welcome such observations, there are a number of reasons it’s better to take a different approach when you’re tempted to praise someone’s weight loss.

1. They may be ill or experiencing a crisis.

Because thinness is valued in our society, when someone loses weight, the assumption is that it’s intentional and healthful – but that’s not always the case. Recent research, funded by the National Institutes of Health and published in the British Journal of General Practice, found that unintended weight loss is an early sign of several forms of cancer, including prostate, ovarian, lung, pancreatic and colorectal.

Also, while many people respond to intense stress and anxiety by eating, others have the opposite reaction, because part of the body’s normal “fight, flight or freeze” response is to shut down digestion.

That noticeably thinner co-worker could be coping with a personal crisis – a painful divorce, a serious illness in the family – and losing weight unintentionally. If you are not privy to that information and offer what seems like an innocent compliment, you may add to their pain.

2. They may have an eating disorder.

In her 2015 book “Body of Truth,” author Harriet Brown writes about how women would approach her then-14-year-old, praise her thin body and ask for diet tips. That’s really not appropriate in any circumstance, but it was especially unfortunate in this case: The teenager was grappling with anorexia nervosa, which severely threatened her health.

For someone who is working on recovering from anorexia or bulimia nervosa – another life-threatening eating disorder characterized by binging and compensatory behaviours like self-induced vomiting – weight loss compliments can be problematic in several ways.

Although anorexia, like other eating disorders, is complex and multifaceted, one factor that can encourage the progression of the disease is positive reinforcement. By praising someone for losing weight when – unknown to you – they have anorexia, you are rewarding them for a behaviour that could eventually kill them.

And you can’t tell who has an eating disorder by looking at them. People of all body sizes can have anorexia – the term “atypical anorexia” refers to people who engage in severe food restriction but are not low-weight.

3. They may have a history of trauma.

There are many ways in which women – and men – are made to feel that their bodies are not their own, or worse, are to blame for bad things that have happened to them. People who suffer childhood sexual or physical abuse, or unwelcome attention to their changing bodies during puberty, may feel shame and guilt and may avoid calling attention to their bodies for decades to come.

I have had several adult patients who after losing weight because of better self-care – improving sleep, reducing stress, eating on a regular schedule and moving more – dropped their new habits when they receive a well-meaning comment because they were so uncomfortable about the focus on their bodies.

4. Body comments may be inappropriate or unappreciated.

In the age of #MeToo one shouldn’t have to explain that unsolicited comments about anyone’s looks are a bad idea, especially in the workplace. And this goes no matter who is making them.

A female colleague related a story about a fellow (female) employee, whom she had never spoken to, passing by her desk and saying, “You look great. Have you lost a ton of weight?” As my colleague had not lost weight, this was probably a case of mistaken identity. Still, she felt it was deeply inappropriate for someone to comment on her body in the workplace.

5. It’s a backhanded compliment.

The implication of “You look great. . . . Have you lost weight?” – no matter the intention – is that you didn’t look good before. Given that most person who lose weight gain at least some of it back, how are they going to feel when that happens? Along those lines…

6. It might not be true.

Complimenting someone on nonexistent weight loss may cause them to start questioning their appearance, wondering if their clothing choices have been unflattering, their posture that bad, their demeanour downtrodden.

7. They are a full-fledged human being – not just a body.

I don’t know who coined the phrase, but we are more than just our Earth suits. Bodies – especially women’s bodies – are too often treated as being fair game for discussion and commentary. Comments like “Have you lost weight?” are not much different from catcalls on the street or a stranger feeling they have license to touch a women’s stomach just because she’s visibly pregnant. Each person deserves body autonomy, and that includes not having their body be a topic of discussion unless they indicate such a discussion is welcome.

What to say instead

Fortunately, there are many ways to be kind, pay a compliment or initiate a conversation. Tell a friend how nice it is to see them. Compliment a co-worker or acquaintance on their style (“Great scarf!”). Or, pair a “How are you?” with a “You look really happy” or “You seem super energetic today!”