Is it realistic to get much faster just by dropping weight as a masters runner?

First of all, you’re 6 years away from being a masters runner. That aside, congratulations on the progression; that’s a big drop over two years. Physics will tell you that lighter is faster, but it’s more complicated than that in reality. You left out key details. How tall are you? How many miles a week are you running? How out of shape were you when you started? Maybe 170 is close to your ideal weight. Hard to know. From experience in the first half of my 40s, I got closer to ideal race weight as a natural result of increasing the volume. I’m 5’11.” At the start of getting into running, I was at 165-170. When I got fit, I was down around 160 (say 50 mpw); very fit 150 - 155 (60-65 miles a week); and near ideal race weight (below 150) for a very short time averaging above 70 mpw. Span of 5 years. I never tried to lose weight through calorie deficit (for me, the training allowed me to eat well), but I did cut out nearly all processed foods and watched my sugar and alcohol consumption to avoid empty calories. Your mileage may vary.

News flash, every pound counts and (unless you’re a walking skeleton) lighter is faster.

Yes it's realistic and very likely. Why don't you just lose weight and find out?

I've always heard 2 seconds (faster) per pound lost per mile.

Masters is 40+ in the U.S. but 35+ in some other countries (I think UK & Commonwealth).

While in principle you may get faster by losing weight, if you actively try to push your body below your "natural" weight, the risk of injury skyrockets. Also, your training may suffer because of low energy levels/low iron/messed up metabolism and you may end up running slower. There is not a "healthy way" to do it. If you were a professional athlete that needs these extra 3 seconds/mile to hit an olympic qualifier and you have a physician monitoring you 24/7, maybe you could justify the risk, but for a master runner?

As others have mentioned, if you run 50+ miles/week and eat a balanced diet, your weight will take care of itself and stabilize on what is optimal for you. I would not overthink it and look elsewhere for improving your times.

If you're lifting to look good with your shirt off, you need to choose between that and running. Excess upper body weight doesn't help running and running doesn't make you look better with your shirt off.

I beg to disagree.

Weight means little without height. If you're 7' tall, 170 pounds is pretty skinny. If you're 5'3" tall...170 is a load.

Spoken like a modern American.

I’ve run a few marathons under 2:30 from age 31 to 39, and while I do train pretty seriously (mostly doubles & 100+ mpw), I find my weight to be probably the most important factor in my race times these days. I try to get to 140-142 at ~5’9”. when I race above 145 I’m usually pretty disappointed in the results, even if my workouts are fast.

What the hell is "fat weight"?? How about just dropping weight...no?

34 is not a masters runner ...

When you get to be a masters runner you'll see that it's easier to run two hour runs than it is to lose weight.

If you could excise 10lbs of fat from your stomach, then you should theoretically be able to shave 10 mins off your marathon time overnight, kind of like taking a weighted vest off. But in reality it is a bit more complicated and depends where you are starting.

If you are average height of 5'10" and 170lbs, then losing 10lbs is almost trivial by making small diet tweaks (avoiding alcohol, cutting back on sweets, etc.) Your performance will likely get better even while you are losing weight.

If you are 6'5" and 170lbs then it's going to be a lot harder to shave off those 10lbs and you may very well see a performance decline, at the very least while you are cutting weight.

Sub-20 BMI in my experience can get pretty dicey.

1. You are not a master's runner.

2. You will benefit from losing weight.

3. At 34 you don't even have to work that hard to drop a few pounds. Here's your formula: up the mileage, cut out a few beers/soft drinks.

Less weight is good. Think about the VO2 max equation. KGs are on the bottom. As long as you are not underfueled you should get faster. Thats the hard part, losing weight while fueling properly.

Yes, but don't starve yourself. Just increase your easy training volume and activity however much you can (just walking more can help a lot), while keeping your dietary intake roughly the same.

The only dietary change I'd try to make is cut down on any unnecessary liquid calories, alcohol soda etc, and sugary snacks. Eat bigger meals instead if your appetite is an issue.

If you increase your training volume while keeping everything else similar otherwise, the weight will gradually come off and your performance will improve (and not just because of the extra training).

Internationaly you are a master when you are 35. There are WR:s from age 35.

how many fat runners do you see running up front?

why would you even ask this question since the answer is so darned blatant?