Does muscle really weight more than fat?

Thanks everyone, my first week was just my first week training, i've been doing this a year come Sept. and was stcu for 4 months with no weight loss, so I decided to hire a trainer. I'm not sure the first week was water loss but the boost in activity, either way, i'm sure it will balance out and I'll start moving the scale again. I'm not going to worry about it, just going to continue.

Thank you all!!!

I started with a personal trainer a few weeks ago. My first week i lost 3-1/2#'s, now this week he has been working me really hard strength training and I show i'm up 2#'s and there's no way I should be up considering my diet and just the sweating alone. It discouraged me. A co-worker said it could be muscle gain but I don't buy it. i'm sticking with it no matter what, maybe i'm just retaining water. I'll be drinking it like a fish the next week.
So my question, is it possible it's muscle gain.????

WIth regard to the eternal "can you build muscle whilst on a calorie deficit" question the answer is yes, but only in specific circumstances.

In the Wallace study (Wallace, M.B., Mills, B.D., & Browning, C.L. (1997). Effects of cross training on markers of insulin resistance/hyperinsulinemia) a group of 8 men lost an average of 16.3 lbs of fat whilst gaining 9.5 lbs of lean mass under clinical observation over a 14 week period.

However, it should be noted that these men were borderline obese with BF% of around 27 and new to training. Also, the figures cited were an average: some lost more and some less due to genetic factors. In addition, whether this rate of fat loss and lean mass gain would carry on at such a rate once their bodies had adapted to the training is highly dubious.

Other circumstances include where an individual can lose fat whilst gaining lean mass are formerly athletic individuals coming back to training after a layoff. However, their figure will be nothing like the above.

If you don't fall into the above categories then it is highly unlikely you can gain lean mass at the same time losing fat whilst on a calorie deficit.

Like the vast majority of questions in fitness this one is individual specific.

ETA: in the Wallace study the water displacement method was used to calculate changes in lean mass (thank you Archimedes...) This is subject to error but better than most methods.

There is a time when you are building muscle and the muscle is coming on to your body faster than you are burning the fat. You can sometimes see an increase in weight during this time, but at the same time, you can see inches coming off of your body because the muscle is more dense. As you gain muscle, it is more effective at burning calories than fat, and you will eventually see the fat burning faster because of your increase in muscle. Everybody's body is different, so the pace this happens for you will be different than for me, your cousin, or someone else on this site.

Back to saying the building muscle on a calorie deficit isn't likely. You need a surplus.

A pound of muscle is about 600 calories. If you broke that up into strictly protein grams it would be 150 grams. That would mean you would have to ingest 150 grams of protein extra ABOVE what your normal protein intake is and have it all convert to gain a pound of pure muscle. Carbs and fats DO NOT BUILD MUSCLE. You cannot convert carbs or fats into protein.
We are now also talking about converting that 150 grams into pure muscle, which isn't likely. Some of it will be excreted out of the body. And adding muscle will usually mean adding about .3 pounds of fat or more.

So let's dispell this myth that people are building muscle while they are working out and on a calorie deficit.

You can, as long as you are training properly eating properly, and have enough body fat reserves. I actually did this. I was obese, on a caloric deficit and used a heavy 5x5 program and gained bout 7lbs of muscle while losing fat. Now, that method is not sustainable for long, I am pretty much on strength maintenance at this point because my body fat percentage is lower. But generally speaking, it is not common.

An OBESE person, a totally untrained person, a returning athlete after a long layoff can add a small amount of muscle on calorie deficit. This was stated on the above pasted clinical study. However we're mostly talking people in the overweight category. Props to you, but much of this "you're building muscle" being attributed to not losing weight is BS.