You will open up a flood gate of responses on this.  I might suggest you type this in the "search" field, get comfy and remember to come up for food and water!

My personal 2 inputs are as follows:

1.  It depends on what level of fitness you are currently in ->i.e. for me it didn't matter which one was "more" correct; I could barely walk at 4.0 for 15 minutes let alone a "High" intensity.  So based on my personal fitness, I had to stay at the 65%-70% Heart Rate zone.  Now, as my body has become more efficient I can do 45 minutes in the 80% + range 4x week no problem.  Overall, calories burned are calories burned so PLEASE don't get hung up on fat burning zone vs. cardio zone - pick what you body is telling you can do as a baseline and then improve on it.

2.  I believe as important - invest TODAY in a POLAR heart rate monitor.  You can live on that treadmill, but if you are not getting your Heart Rate up into the 'zones, the scale ain't gonna budge (pardon the grammer).  The POLAR will at least allow you to know that the time spent on the treadmill is at least moving  you towards your goal.

Best of luck, and stick with it!

Giving intensity guidelines is a tough call since a lot of it will depend on your fitness level - What you should be aiming for while you work out should be this:

You should feel as though you are breathing heavier than usual - you should exerting yourself so that you are still able to carry on a conversation with someone - but perhaps feeling as though you would rather not be carrying on a conversation!

I would probably lean towards the lower intensity for longer durations as long as this challenges you.

You might want to try monitoring your heart rate to also help in determining if you are working in the right intensity level.

Also you haven't mentioned adjusting your eating habits? Monitoring what you are consuming is KEY in seeing results. Exercise is fantastic - but in my experience you need the combination of eating habits and exercise to have the biggest effect on your weight loss.

Thanks for the replies...

Yeah I have adjusted my eating habits, cutting out all junk food, fizzy drinks etc. Eating fruit, veggies, which I wasn't doing very often before!

My fitness is improving now, when I started the gym 3 weeks ago it was the first time I'd exercised in a while, but I can quite happy stay on the treadmill for 50 minutes now whereas 3 weeks ago I could only do 20 mins...

I dont understand the whole heart rate zone thingy thought

Check out this short article on measuring your intensity using your heart rate:

http://exercise.about.com/cs/cardioworkouts/a/ex_intensity.h tm

There are lots of online calculators available to help you determine where you should be.

Glad to see you are seeing at least some improvement in your fitness level if not immediately on the scale. At the VERY least you are improving your heart & lung health with your current exercise schedule!

Original Post by jef9up:

I would probably lean towards the lower intensity for longer durations as long as this challenges you.

Agreed, keep that pulse up for a while and thats the most effective, I just started a new cardio which is jogging for 20-25 mins then doing 10 mins of incline jogging/running and running up stairs in a local parking garage that is closed.  I know that sounds weird but you can get alot done in a parking garage like stairs and incline. amm I crazy? lol

UGH.

Long, steady state cardio has been proven to be the LEAST effective exercise. Ok great you burned 400 calories lumbering around on a treadmill for 45 minutes. You'll get the exact same result by cutting out 400 calories of crap from your diet.

HIIT and intervals are best for weight loss, with HIIT being the big granddaddy. If you're really serious about fat loss (not weight loss, but just the pesky FAT), you lift weights.

In order of effectiveness for fat loss:

#1. diet
#2. weight lifting
#3. HIIT

and about 50th down the list is steady state cardio

READ ME

Do you hang on to the bars of the treadmill at all while you are walking/jogging?  If you do, your calorie burn is probably significantly less than what the machine is telling you. 

Also, just because you are eating more fruits and veggies doesn't mean you are automatically going to lose weight.  It's all about calories in vs. calories out.  Your lack of weight loss points to diet issues and not exercise issues.

i know that lots of people on here will say steady cardio is not effective for fat loss.  and inevitably, they'll follow that up w/ lots of research articles and quotes to illustrate for you just how effective weight lifting is.  that's fantastic.  weight lifting is awesome and you should do it. etc. etc.etc.

okay but about your question -- i can only speak to my experience (i have no research on this, just some friends who run marathons): doing longer but slower runs are more likely to increase endurance.  doing shorter but more intensive runs will increase your speed.  your fitness will be increased just by running!

in my experience, i have lost my love handles after running longer amounts of time.  i love to run....as i keep increasing my mileage and time, 6 or 7 miles usually, my body is changing.  my love handles are smaller and my legs are slimmer.  i like how i look when i run consistently, like 2 or 3 times per week, but i also go to the gym and play competitive field hockey the other days.  but i really have noticed that RUNNING makes a HUGE difference!!  i would continue running....for as long as you can.  increase your speed every so often but keep running if that's something you enjoy and can stick with.  good luck!! 

alternate it AKA HIIT. read all about it at http://bodybuilding.com/fun/bbinfo.php?page=HIIT its really intense, but you get used to it

Original Post by jes516:

i know that lots of people on here will say steady cardio is not effective for fat loss. and inevitably, they'll follow that up w/ lots of research articles and quotes to illustrate for you just how effective weight lifting is. that's fantastic. weight lifting is awesome and you should do it. etc. etc.etc.

okay but about your question -- i can only speak to my experience (i have no research on this, just some friends who run marathons): doing longer but slower runs are more likely to increase endurance. doing shorter but more intensive runs will increase your speed. your fitness will be increased just by running!

in my experience, i have lost my love handles after running longer amounts of time. i love to run....as i keep increasing my mileage and time, 6 or 7 miles usually, my body is changing. my love handles are smaller and my legs are slimmer. i like how i look when i run consistently, like 2 or 3 times per week, but i also go to the gym and play competitive field hockey the other days. but i really have noticed that RUNNING makes a HUGE difference!! i would continue running....for as long as you can. increase your speed every so often but keep running if that's something you enjoy and can stick with. good luck!!

Studies with lots of participants be damned, we have this one person's experience!

Original Post by jes516:

i know that lots of people on here will say steady cardio is not effective for fat loss. and inevitably, they'll follow that up w/ lots of research articles and quotes to illustrate for you just how effective weight lifting is. that's fantastic. weight lifting is awesome and you should do it. etc. etc.etc.

Catabolic exercises like long-distance running break down muscle over time (the body works to streamline the athlete for the task at hand), which can lead to a high percentage of body fat—compared to other athletic individuals.

I stick with weight training and cardio that builds muscle rather than breaks it down—sprinting being one example. And certainly, if running is all one does, weight training should be added to maintain the muscle that person already has.

As for endurance, short bursts of highly intensive exercise are being shown more and more to significantly impact your endurance, too. (Oh, no: here comes one of those studies. ) This is just one of myriad articles you can read about that:

http://sportsmedicine.about.com/od/sampleworkouts/a/30sec_sp rints.htm

I am 5' 3 1/2" and 110 lbs, and got there via a proper diet, weight training, and cardio designed to build muscle and endurance both. My body-fat percentage is very low, much more that of a professional athlete than that of the average 35-year-old woman.

lol

For males, it is crucial that we avoid the high beats-per-minute range because in that range, a person begins burning fat and muscle.  For females however, tone is more important than muscle mass.

I recommend high intensity cardio (running, plyometrics, tae-bo) and light weight-lifting (light freeweights, yoga, pilates) sessions.  You will burn the most calories at higher intensity and although you will lose a small amount of muscle mass, the added weight-lifting sessions will tone your arms, back, legs and butt.

If you don't want to lose any muscle mass, then do lower intensity workouts (power walking, etc).

Original Post by melkor:

Ahem. And what exactly would "tone" be?

There is zero, zip, no, nada difference between the skeletal muscle mass of men and women, and there's no difference in the way men and women should train. Anyone thinking differently has read too much Shape and too little exercise physiology.

Indeed.

There is no reason for women to fear higher weight/lower reps. I have been lifting for 18 years—I lift as much as I can every time I work out—and I still look like a woman. We are not designed to bulk up.

I read this article the other day, maybe it helps?

I disagree completely.  Yes, our bodies function the same way, but men and women have ENTIRELY DIFFERENT goals in terms of how their bodies should look.  All I was saying is that males don't typically want to lose muscle mass by doing exercises that put their heart rate in the cardio range.  Females, on the other hand, are less concerned about building huge muscles and therefore are more inclined to choose high bpm workouts.  There is no disparity between how men's and women's bodies function.  The only disparity is in their goals and the majority of women I know don't want 17" biceps.

Original Post by dcyounts:

I disagree completely. Yes, our bodies function the same way, but men and women have ENTIRELY DIFFERENT goals in terms of how their bodies should look. All I was saying is that males don't typically want to lose muscle mass by doing exercises that put their heart rate in the cardio range. Females, on the other hand, are less concerned about building huge muscles and therefore are more inclined to choose high bpm workouts. There is no disparity between how men's and women's bodies function. The only disparity is in their goals and the majority of women I know don't want 17" biceps.

Huge muscles? 17" biceps? I work out more than anyone I know, male or female. I have for 18 years. I lift heavy weights, too. And I do not have 17" biceps. It is not physically possible. I have a slender physique with definite but delicate muscle, period. Very few women are going to end up muscle bound without the use of steroids.

Certainly, I understand that many women are not into muscle at all, or only want a little to show (though just as many ask me all the time how to get my arms...). But saying that muscle mass is more important for men is an absolute falsehood. Muscle mass is essential for everyone for long-term health and fitness. And it is OK to push yourself in the gym as a woman: it does not mean you will turn into the Incredible Hulk. Far from it. Please do not perpetuate this myth and frighten women off from lifting real weight.

As for goals.... My goal is to be able to eat throughout the day without fearing I'll gain weight. My goal is to fit into smaller clothes (while, again, eating when I want, without fear) because muscle is denser than fat. And more important by far, my goal is to be able to enjoy an active life as I age. My goal is be able to recover quickly—recover, period—should I fall due to the cells in my inner ear that regulate balance dying as I age. These, and more, are my goals over the long haul.

These goals require muscle mass to be fulfilled. (Bone mass, too—something else that weight training delivers.) And after the age of 25, men and women both lose as much as 5 lbs. of muscle mass every decade. If you engage in a lot of catabolic exercise and don't weight train with real weight, you'll lose even more. This has real consequences—for both sexes.