How long does that first 7 miles take you? Do you eat before you run, or are you going out on an empty stomach? Do you eat anything during the run for fuel?

Speaking very generally...
Will the deficit matter? Yes, but you can work with/around it and still be good for moderate length runs (in my experience). The bigger picture is that nothing about your diet lends itself to endurance training - low cals, little to no complex carbs. If you want to maintain that kind of diet, you'll likely have to be more diligent about your intake before and during your runs.

Have you tried eating close to when you run, or eating during the run to see if that changes how you feel? I have been using fruit as fuel during my runs, and I like it better than Gu type products. During the summer I freeze grapes, and then by mid run they are thawed. It's really refreshing. Now that it's winter it won't really work as well. Also mandarin oranges are portable, and easy to peel while running.

mkakids wrote: »

I'm training for a half marathon at the end of November. My longest run so far has been 10 miles.
Each time I'm out for more than 7 miles - the last few are BRUTAL.

I'm just wondering if my eating at a deficit (fairly large one considering I've lost 20# and 22" in the last 12 weeks) is the issue, or if its simply a lack of experience running distances greater than 6 miles. I also eat semi low carb.....averaging about 75- 125g a day. I don't restrict carbs...I just don't reach for them often. I rarely eat bread/grains (just not my thing), but do eat alot of fruits and veggies...and more candy the last few days than I care to admit, lol.

I've been running regularly for about 2 years, an my long runs usually are 5-6 miles....but now that I am training for the half in a few weeks...those have obviously been increasing (as well as the number of weekly runs in the 5-6 mile category).

I'm going to take a wild guess here . . . I bet you're running without mid-run refueling, and it's catching up to you about mile 7. This is unrelated to eating at a deficit overall; running without refueling would catch up to me about then, and I'm eating to maintain my weight.

A long run of 5 or 6 miles without in-run fueling is manageable for most runners. Beyond that, somewhere you run out of glycogen and start really hurting. How far beyond that? Depends on the individual, how hard the run is, what the weather is like, how well you ate before running, how well hydrated you are, etc. If you're going to run the half marathon distance or longer, you need to pay attention to what your body needs during the run.

One size does not fit all. I follow a discipline of a gel every 5 miles. I have a sister who takes a gel before the race, then starts in on shot blocks at mile 6. Some runners go by time, some go by distance. Some people do well with real food instead of gels or chews marketed for running. You need to find what works for you, by experimenting and discarding the things that don't work.

Eating at an overall deficit might also impact performance for endurance runs; but if you're more concerned about finishing than about time, that's not going to be as immediately obvious as the effect of in-run fueling.

There is also the chance that hydration and/or electrolytes could play into what you're feeling. If you're not getting enough water, or if you're depleting your electrolytes and not replacing them well enough, that could also have the results you describe for over 7 miles.

Good luck figuring out what is wrong and getting it corrected!

mkakids wrote: »

Anything less than 5 miles, I don't fuel mid run. Over that and I generally fuel around mile 3 (approx 35/36 minutes in) and every 3 miles after that. I've tried a variety of fuels. Gu, sports beans, cliff blocks, gatorade chews, honey stingers, honey sticks, jelly beans, smarties.....I've never noticed a difference. I carry water with me over 5 miles and drink every 2-3 miles.

Depending on weather and how your body reacts, that may or may not be enough hydration. If you're not noticing a difference with fueling, either you're not eating enough or eating isn't the issue. Best guesses from what you've shared to date:

1. Running too fast, as described by other commenters. Long runs should be "conversational," meaning you can have a conversation with running buddies. If you run alone, there's the Pledge of Allegiance test: If you can't recite the Pledge of Allegiance while running, in the cadence you learned in school, without taking more breaths than you used in school (3 in my case), you're running too fast. If you have to gasp for breath in the middle of a phrase, you're running WAY too fast. [If you're not an American, or if they phased out the Pledge by the time you were in school, any liturgical recitation will do. The Lord's Prayer, if you are of the Christian persuasion. A favorite poem you learned in school. A page or two from a Dr. Seuss book that you remember. Whatever there is that you know that is comfortable for you.]

2. Electrolyte depletion. This is more likely if you're following advice commonly given for weight loss to limit sodium intake. You get some electrolytes from the GU, sport beans, etc., but it may not be enough. You might want to try a low cal/no cal electrolyte drink while running. I use Nuun, but there are other brands that should be similar. I find I do better with a half tablet of Nuun on a 10 mile run than with just water; and I have way more sodium in my normal diet than most people who are following the common wisdom of how to eat healthy.

3. You're simply not conditioned enough to run much beyond 7 miles. The cure for this is to run a bit past 7 for a while till that's comfortable, then gradually increase the length of runs. I'd rank this as the least likely, but it is possible.

So how do you tell what it is? You just have to try stuff to cure one thing or another, and see if it helps. Different runners react differently, and need different levels of nutrition, hydration, and electrolyte replenishment. You have to find what your needs are by trial and error. The "error" part can be uncomfortable, so you want to be paying attention and hopefully learn something from it.

MobyCarp wrote: »

A long run of 5 or 6 miles without in-run fueling is manageable for most runners. Beyond that, somewhere you run out of glycogen...

Glycogen depletion doesn't typically happen until between 90 and 120 minutes of continuous exercise in most recreational runners and much later than that in well trained distance runners.