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My BMI is 26.8, which means that I am in the overweight category.

When one hits a gym regularly every day, what is the minimum amount of calories that he should burn in order to see a change in his weight over a month's time? I generally focus on simple exercises like being on the treadmill for around 20mins (150 Cal) and on the cross trainer for 20mins as well.

Is this enough or should I increase my workout?

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5 Answers 5

up vote 21 down vote accepted

1 kilo fat equals 7000 kcal or 1 pound fat equals 3500 kcal, so if you keep your diet the same and start working out more: that's how it takes to loose a kilo.

So assuming your 2 workouts burn 300 kcal together, you need 7000/300 = 23.3 workouts to loose a kilo. That would mean you would have to train nearly every day of the month to loose it... Clearly, that's not really an optimistic goal to work towards, though on the other hand: it's easier to keep up since you don't have to eat less (but not more!) and the result is probably more sustained than with some crash diet.

Off course, increasing the intensity or the duration will chance those numbers, but adding more 'exercise' is a more effective way of increasing the amount of calories burned in a day: cycle to work, take the stairs, take a stroll during lunch, etc.

Your other option would be to consume 200 kcal's less each day, which would also result in a 1 kilo difference. So doing them both, would probably give you quicker results. Funny enough if you add those two, you get the 500 kcal that @Campbell mentioned, so I guess his estimate seems about right.

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+1 - and for those who can't do the math: The simple American conversion is: 1 pound of fat = 3500 kcal –  Nathan Wheeler Mar 3 '11 at 17:06
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-1 All nice ideas, if true, but there has never been a clinical trial where anyone lost 1 pound for every 3500 kcal deficit, or even close to that. –  michael May 9 '11 at 17:31
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In the ATOZ diet study, jama.ama-assn.org/content/297/9/969.full people with an average weight of 180 lbs kept a calorie deficit of > 350/day calories for a year and lost an average of 6 lbs. They should have lost 36 lbs. That is more than a mis-estimate. Every other study shows similar issues. –  michael May 9 '11 at 18:12
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Exactly; the body will change how much energy it burns depending on how much energy is consumed in ways that we have no control over. Therefore, 500kcal/day = 1 lbs is the a completely useless estimate, especially in the long term, as shown in study after study. (note that in the ATOZ study, max weight loss was reached in 3 months and weight was gained back after that, despite a continued calorie deficit.) –  michael May 9 '11 at 18:25
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No one is saying that you lose 1 pound for every 3500 kcal deficit. They are stating how much energy is stored in 1 pound. Think of it like this: A mile is 5280 feet. Just because you walk 5280 feet doesn't mean you are displaced by a mile, it means you walked a mile. It is a unit of measure, not a one-to-one. If someone took a 200 kcal food out of their diet and started exercising (burning 300 kcal/session) theoretically they should lose 1 pound per week. 500*7=3500 We know this isn't how it really happens, but it is a good benchmark. –  Grohlier Jan 10 '13 at 18:43

Bad Metrics

It is vitally important that you not base your workout on BMI.

Please read Slate's excellent discussion of how BMI came to be used to poorly and NPR's 10 Reasons why BMI should never, ever, really-don't-do-it, never be used for one's self-image or exercise goals.

BMI is not a valid way to measure your fitness or body. It is not useful for that purpose. Using it to measure how much weight you should lose, or how many calories to burn, is a surefire way to disappoint yourself.

Examine.com has a good overview on the validity (and lack thereof) of BMI, which can be summarized thus:

If you are normal weight or overweight according to BMI (18.5-29.9) there is still a chance you are actually obese, and thus is primarily due to low levels of lean mass (muscle, water, and glycogen).

...

Outliers to this dataset, those who have enough lean mass to be classified as obese by BMI but not by body fat percentage, are far and few in society. These persons would normally be highly active athletes or dedicated 'weekend warriors', and it is unlikely sedentary persons or those with infrequent exercise habits would be these outliers.

Good Metrics

Instead, measure what you want to improve. Want to look better? Get a camera and a tape measure and track how you look (with consistent clothing, pose and lighting) and measurements of your arms, legs, hips, and waist.

It can also be more productive to set a performance goal. Good goals can be based around time ("run a mile in less than 7 minutes"), weight ("squat with a barbell as heavy as I am"), or simple completion ("finish a 5k"). This will shape your training in a way that makes you more fit, while also restructuring your body.

If you absolutely must have a science-y number to track, the Body Shape Index, which uses BMI but isn't directly correlated to it, and seems to be a better predictor of one's risk of death. Keep in mind that while it takes belly fat into account, it still does not keep track of muscle or actual markers of physical health, like mobility, strength, inflammation, diabetic state, or cardiovascular disease.

Body Shape Index= Waist Circumference/[(BMI^(2/3))*(height^(1/2))]

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Also worth noting that the epidemiological studies used to "support" the notion that being "overweight" (BMI 25-30) is bad for your health, actually showed people with BMIs from 25-27 with the lowest death rates. The proponents of BMI as a predictor of health and life expectancy don't even follow their own data. –  Robin Ashe Jul 27 '12 at 0:07

Here's something most people don't know: when people say that 1 pound of fat is 3500 calories, that's not actually true. Or rather, it's not the whole truth.

You see, 1 pound of fat is 3500 calories only in an oven. That's how we determine how many calories are in a given food: we burn that food and measure how much heat is produced as a result. We can't do that in a human, so we have to do it in an oven.

So counting calories most of the time is of limited use to people. Why? Because you can have 2 people who are identical in weight, age, sex, exercise levels, stress levels, etc.. But feed those 2 people the exact same number of calories and I can guarantee that those 2 people will NOT gain the same amount of weight. One may gain nothing and the other may gain 3 pounds. Or one may lose 3 pounds and the other doesn't gain anything.

We all know someone who can eat whatever they like and not put on an ounce of fat, and then there are most people who actually have to watch what they eat to remain at a certain body fat percentage.

Body fat and weight are much more strictly controlled by hormones than by calories. There is a YouTube video of mine that explains it pretty well.

Also, by doing excessive and exclusive cardio, yes, you may be burning calories during the workout, but due to a process called "adaptation", you burn fewer and fewer calories each time you exercise. You learn to become "fuel efficient." Doing excessive and exclusive cardio has a double whammy of also burning muscle. Muscle burns fat, so if you have less of the "machinery" that burns fat, you burn less fat.

What can happen over time is that your weight is "normal" yet your body fat is extremely high because you've burned a lot of muscle.

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Welcome to this site, we need experts like you. Please post some links to research which supports your answer, so we can evaluate the source material. And please be persistent, you will be fighting some headwinds made up of "common knowledge". –  michael Jul 31 '12 at 2:02

It depends on how many calories you consume.

Use a tool like FitDay to track both your calories in and your calories out. You should aim for a daily deficit of around 500 calories per day. Be careful to avoid any more than that kind of amount as you will trigger your body in to starvation mode, get low energy and find it difficult to shift weight.

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Your "be careful" statement only holds true if the person is consuming (for example) 1100 kcal per day. If the average person was consuming 3500 kcal per day they could afford to cut out more than 500 kcal per day. I know there are exceptions to every rule: Michael Phelps' (for example) caloric intake is approximately 11,000 kcal per workout day, but it is because he uses 9,000 kcal to perform his training. –  Grohlier Jan 10 '13 at 19:18

A pound = 3500 calories. So creating a calorie deficit of 500 a day (either by consuming less or burning it off) should result in a pound lost per week.

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+1 - simple and to the point. I like it. –  Nathan Wheeler Mar 3 '11 at 19:44
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-1 Simple, but wrong. Show one clinical trial where people lost the amount of weight predicted by their calorie deficit. You can't, because it does not exist. –  michael May 9 '11 at 17:30
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I am very influenced by Gary Taube's work, but there was a recent study that showed that as sugar consumption decreased in Australia over 20 years, obesity continued to increase. The study (The Australian paradox) suggests that sugar was replaced with artificial sweeteners, but that isn't entirely clear. Taubes thinks that there is a threshold of sugar that they stayed above which caused weight gain. My guess is that sugar and artificial sweeteners are both too processed for the body to deal with correctly. Maybe someday we will know what is really going on. –  michael Jul 10 '11 at 22:42
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@Joe I am fortunate that I have never been overweight, so I can't draw on personal experience. But, if I was to suggest to someone else, I would say, "Cut out all sweeteners and cook everything from scratch yourself." Or try paleo. I don't think my advice is worth much though. It's just a guess. –  michael Jul 11 '11 at 12:58
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This is a very intriguing conversation and I'll look more into this notion that there's no clinical proof that 3500 kcal deficit equals 1 lb lost. But I, for one, have actually been overweight, "obese category II" to be exact. And I was put on a doctor supervised 850-1000 kcal/day high protein diet plus resistance training and 5 months later I am 5 stone (c. 70 lbs) lighter. The whole program is based on the -3500 deficit notion and my own BMR. And it all worked to a mathematical tee. So in this human body at least, the 3500 = 1 lb decifit theory works. –  user3495 Jun 15 '12 at 9:03

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