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I train every day, usually running 4 miles and doing brisk walking on an incline to burn fat. My calorie intake is less than 1500 calories, and I am burning between 500-600 calories per day which leaves me an average daily intake of 800-900 calories.

Is this enough for a 12 stone man (168 pounds) to stay in good health? I've been doing it for 1 month now and am starting to feel a bit tired with my training getting harder?

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Sounds like you're running your body down and not providing it enough fuel to rebuild itself. What's your diet consisted of? –  DForck42 Sep 5 '12 at 20:18
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Are you still at 12 stone or have you lost a lot of weight due to the very low calorie intake? –  Usedtobefat Sep 5 '12 at 21:55
    
That's a really low net Calorie intake. You'll lose weight fast, but your body's Leptin levels (and a few other hormones/neurotransmitters) are going to force you into a starvation state. You'll be more efficient with the Calories you intake, but the moment you reach a Calorie surplus you'll be more prone to regaining weight. Your training might be getting harder because your body is burning muscle to feed itself while you work out, especially if your workout is more than about 20-30 minutes. –  MCM Sep 7 '12 at 3:59

4 Answers 4

Personally I would say no, this is not enough to stay in good health. I would say that you are not consuming anywhere near enough calories. I am surprised you are only starting to feel the effects of this now.

Assuming you are a male, I would recommend that with doing that amount of training you should consume (cleanly) closer to 2500-3000 calories. This is taken from the UK Department of Health Estimated Average Requirements (EAR). Its an average, so there are other factors to take into account(age, height etc), so you should use it as a guide.

With this you will notice that you will have more energy.

Also make sure you are getting enough rest. 8hrs sleep on average. And dont be afraid to take the odd day off to allow your body to recover. Exercising everyday for a month will have a big toll on the body, so rest plenty.

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The goal is to lose weight, so his actual target caloric range (based off the very source you linked) should be 2000-2500. With a 3000 calorie diet and 500 calorie exercise it is unlikely to promote any fat loss. –  Moses Sep 18 '12 at 18:32
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At 12 stone (168 lbs), he should instead focus on recomposition (i.e. maintaining weight while getting leaner). –  Berin Loritsch Sep 19 '12 at 12:47

The training is harder because you probably have depleted all glucose in your body. Your body have a hard time functioning since it have no readily available fuel and tries to use your fat store for energy.

You don't write your height or fat% but assuming you are around 175cm, you probably are pretty low on fat mass, and is probably metabolising muscles as well.

For this reason I would advice against this. Having muscle mass is a good thing and is something you should hold on to.

If I where to guess you probably have a daily expenditure of around 2500-3000 kcal depending on how much you move around apart from your active exercise. In that case I think you should be eating 2000-2500 kcal per day, and if you are not losing fat mass. Start cutting from there.

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If the calories for your workout were the only ones burnt per day your math would be correct. However, everyone has a resting metabolic rate (RMR). A RMR is the amount of energy (in calories) it would take for your body to perform the basics to keep you alive (breathing, heart beat, etc.). Everyone's RMR is different, dependent upon several factors (including age, gender, genetics, lean muscle mass, etc.), and can only be calculated via an RMR test. Unless you have thyroid issues your RMR is probably in the 1200-1600cal range.

This means with your exercise you are actually burning 1700-2100ish calories a day.

Therefore you are actually a net loss of 200-600 calories a day. With 3500 calories in one pound, you'd be losing one pound every 6 days or so. A lot of other factors can play in to this, just putting the math into perspective.

You are probably tired because you are working really hard and not consuming enough to make up the deficit.

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A mistake a lot of people make is that they assume that the human body is some kind of book keeper. That it counts the calories in and calories out and whats left is the energy you have. Unfortunately its not that easy. There are hundreds and hundreds of other variables that have influence on your energy or health in general.

The biggest calorie burners are your digestion and your internal heating system to keep your body on the right temperature. But it's not about keeping track of the calories. Getting energy is about providing your body with the right nutrients (including water and oxygen) and supporting your body with eliminating the toxins.

If we take a look at our bodies a bit closer you see that your body is build up from cells, those cells provide us with the energy we need (this process is called metabolism). Providing those cells with the chemicals they need and eliminating it's waist products will result in an increase in energy.

Above all cells need oxygen and water, so take deep breaths and eat a lot of foods that contain water (vegetables and fruits). Besides that cells need vitamins and minerals, so make sure you eat a lot of vegetables and take some high quality supplements). And lastly cells need sugars (carbohydrates are converted into sugar) and 'good' fats.

To answer your question, it is very important to listen to your body. If you feel tired you need to make some changes. There are a couple of things you can do. I listed the important ones below, starting with the one with the highest impact:

Study yoga breathing techniques and learn to take deeper abdominal breaths
Eat more water rich foods (at least 60% of your diet should be vegetables)
Sleep more (ideally you want to wake up without an alarm clock most of the time)
Exercise less or less intensive (walking is considered the healthiest form of exercise by many doctors)
Take vitamin supplements and eat more omega-3 fats.

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I wanted to upvote this answer, but then I read toxins. –  Baarn Oct 18 '12 at 20:01
    
Thanks for the comment, but can you be a bit more specific. What don't you like or you think is wrong about 'toxins' (aka waste products)? Thanks. –  Jasper A. Oct 19 '12 at 7:37

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