Can I drink alcohol if it fits into my calories or should I limit it to lose weight?

In 8+ years of calorie counting, I haven't noticed any slowing of weight loss from consuming reasonable amounts of alcohol, when I accounted for the calories. (Other people report differently, but that's my experience.)

Alcohol is devoid of nutrition (actually is poison, technically), so sticking to reduced calories but drinking alcohol can limit ability to get overall good nutrition, which is important for health.

When drinking, it's easy to lose track of food intake, which makes for slips in accurate calorie counting.

Alcohol can reduce inhibition, make it easier to give in to cravings for tempting high-calorie foods, especially in social settings where other people are eating those foods.

As Tom says, drinking can impair sleep, cause lethargy . . . and moving less will slow weight loss no matter what caused the lethargy.

Many people here report doing better with weight loss when they limit or eliminate alcohol. I didn't eliminate it, but did drink relatively infrequently during loss. I've consumed alcohol more frequently in the 7+ years of maintenance since loss, with no unexpected consequences to my body weight. With only rare exceptions, I make sure I've hit certain personal nutritional minimums, and have the calories available to allocate to the alcohol, before I drink it. YMMV.

As far as whether to limit to once a week, or have it whenever you want some, that's your call.

The one thing I'd say is that if you don't plan to give up alcohol forever, it could be a good strategy to figure out during weight loss how you're going to handle alcohol in the long term. Treating weight loss as a special project with an end date, after which things go back to normal . . . that's a recipe for yo-yo regain. Managing alcohol is part of successful weight maintenance, for those who don't choose to give it up.

I have found that a couple of glasses of gin and slimline tonic at the weekend (calories counted) hasn't harmed my loss, but if I do have too much then I get the munchies and want crisps to I am very careful!

My view — fit it into your calories.
If you are losing weight, you may start to realize that alcohol is an empty calorie, so you’ll likely want to reduce it, just like you may want to reduce sugar.

I Love wine but it's not doing me any favors. The reason is I eat so much more on days that I drink. A night of drinking and eating I easily destroy a weeks' worth of calorie deficit. But that is because I can't control myself when I drink. So drinking for me has to be a rare occasion.