I’m gaining weight now that I’m exercising

[WellTidy]

I’ve lost a stone so far this year, another stone to lose before I’m in the middle of my BMI (which I should be - small frame, small boobs, not much muscle, short, mid 40s).

I lost the stone by cutting down on portion size and snacks, not eliminating anything, and also walking around 20 miles a week.

Ive stayed the same more or less for about 7 weeks, so I’ve now joined the gym to try and lose the extra stone. All forms of exercise are new to me so I’ve been doing what I’m comfortable with like walking at gradient, some rowing and some cross-trainer (which I find really hard). Also a bit of yoga and cycling, nothing exciting.

I’ve been on average every other day to the gym for a fortnight now and I am gaining weight. Only a few pounds but is this to be expected? And if so, how long might it last?!

You’re likely building muscle OP and muscle weighs more than fat. But it could also be that due to getting more exercise done you are eating a little bit more and haven’t noticed?
I have lost over 3 stone and in the past 3 years and it has had its ups and downs. When I started lane swimming 5 times a week I was incredibly frustrated to be putting on a few pounds here and there. Then it dawned on me that my body was still changing in a flattering way, so I was building muscle tone. I also increased my water intake to limit hunger a bit more (swimming makes you so hungry in my opinion).
Good luck, give it time and plenty of it!! You will get there.

Muscle is more dense than fat, so if you're replacing the latter with the former it's to be expected.

If you're burning fat but adding the same volume of muscle, it'll weigh twice as much. The picture below demonstrates how.

I try and avoid scales and go by how I look and feel instead Keep it up!

While it's true that muscle weighs more than fat, I'd be surprised if you were building muscle with the exercises you're doing (not a criticism at all but it's quite hard to build muscle). It's more likely to be water retention but is not unexpected.

How much is a few lbs weight gain -- 3? 10?

There are hard physical limits to how much muscle a woman can gain (or lose). You can't turn gain many kg of muscle unless you started bedbound.

Over 7 weeks 1-3 lb extra as muscle might be plausible starting from a low place, with a moderate exercise regime, but not 7-10 lbs.

Agree that it's not likely to be muscle, unless you're really going for it. Do you measure yourself in addition to weighing yourself? If not, I'd suggest doing so. Your weight might increase a bit just because of water retention or some other reason but you could find that you're measurements are de-creasing at a steady pace in line with your exercise/calorie intake.
Also, in regards to your food, do you carefully monitor what you consume or do you just keep a mental note? It's incredibly easy to miss calories that you might not have factored in. Using an app like My Fitness Pal to track every calorie you consume (drink too, not just food) will help highlight if there's something you are eating/drinking that you didn't realise was actually totting your daily total up by more than you anticipated.

Ditch the scales and get a tape measure.

Don't fall into the trap of eating back calories burnt. I used to swim for exercise, now I swim for fun and go to the gym because I eat like a horse after a big swim!

I tend to eat more when I start exercising so I have to count calories or at least be super aware of what I'm eating.

I think it is muscle gain (I am definitely a mesomoprh and gain muscle easily) but it's water retention as well, something to do with muscle tearing then getting stronger. You do need to drink more water but not too much - watch your pee, if it's colourless you are drinking too much water, if it's pale yellow, you're spot on, dark yellow - too little.

When I was younger I would put weight on slightly for two months when increasing exercise, recently it has been more like six months. I've just started to lose weight but have to eat a lot fewer calories at 46 to lose weight than I did at 26.

That is to say, I am eating actually the same amount of calories to lose weight as I did 20 years ago, but I was much lighter 20 years ago to start with.

It is categorically NOT true that muscle weighs more than fat - no idea why that keeps being trotted put as it's a myth as a quick google will reveal.

It is however denser and takes up less space

While it's true that muscle weighs more than fat no it's not, a lb of anything weighs a lb!!
Muscle is more dense than fat so a lb of muscle (as illustrated above) takes us less space than a lb of fat. That said, as women it is very hard to build any serious amount of muscle unless you lift very heavy weights several times a week, eat a protein rich diet, and probably take supplements. The OP hasn't even mentioned lifting a weight so it's unlikely to be that in a short space of time!

You’re likely building muscle OP and muscle weighs more than fat

A pound of muscle weighs the same as a pound of fat. They both weigh a pound.

Sorry, I was one of the ones who said that and you're totally right. I was being very lazy at explaining what I meant and used a shorthand which was very unhelpful.

You’re likely building muscle OP

Nobody puts on several pounds of muscle in 2 weeks doing walking and crosstrainer. Water retention and increased appetite.

This blog talks about women typically able to gain about 0.5 lbs/muscle per month over a 4.5 month period, when they start weight-lifting which is obviously activity focused on muscle gain not cardio benefits. The per month gain in muscle slows down after the first 1-2 months. Because there are physical limits to how much muscle a person can gain, how much body composition altering is possible. MNers talking about 2 kg gains in muscle over short periods make me laugh. Fat people often already have a lot of muscle from hauling all those extra kg around with them everywhere.

darnit, teach me never to use dashes and to preview (!!)

Tired muscles cause water retention as they recover. This is a good process for strengthening muscle long term and the water weight is not harmful. You'll look leaner for it despite what the scales say.

There’s no way you have gained several pounds of muscle in a fortnight.
you may be gaining muscle if you’ve literally never done any exercise before, but not that much.
I’d guess that you’re hungrier and getting a bit slack with calorie counting / monitoring what you eat. Or you could be due on. Or you may be drinking more water.
the gym is a red herring - correlation isn’t causation

Really funny that muscle doesn’t weigh more than fat - a god damn gym instructor told me that just the other day. 😂 😂 Didn’t mean to mislead Op, just trying to be supportive and what I was taught at a gym. Hope you keep up the good work!!

I think it's more likely that the exercise is making you hungrier and you're eating more than you're burning off. Could that be correct OP?

That phrase is just a shorthand way of saying it is more dense than fat, as PPs explained. A lb of a thing is still a lb!

However when the phrase 'muscle weighs more than fat' is used, it's taken that it refers to density.

That is because muscles weigh heavier than fat

your muscles start to hold an extra few lbs of water weight when you're new to working out. if it's under 5lbs it will be that.

God seriously, get off the scales. Do you feel healthier? Are you less out of breath? Are you sleeping better? Weight is pretty unimportant, good health is what counts.

I don’t think you would gain muscle from what you are doing (cardio), if you were doing weights then I would expect a gain.

I exercise a lot and find that it just makes me really hungry so I don’t necessarily lose weight from exercising but it benefits me in other ways and helps tone.

It is very, very common for people to start eating more when they start exercising more, and they don't even realise it.