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Saturday, July 14, 2012

Energy Expenditure: Activity and Exercise (Weight Series Part 4)

Photo by familymwr on flickr

A large amount of scientific evidence supports positive effects of exercise,[1] and the recommendations of doing more exercise are pervasive. Yet a lot of people, and especially a number of dieters, do little to nothing. The question as to why that is the case is part of the central problem of figuring out why so many people are becoming overweight.

As we know, weight and body fat solely depend on the energy balance, that is, how many calories we take in as opposed to how many we expend.[2] While the last post in this series looked at the intake part of the equation,[3] this post will take a closer look at the benefits, myths and approaches to increasing energy expenditure.

Reasons for Exercise

The expenditure part of the energy balance consists of the resting energy expenditure, which is explained in part two of this series series,[2] and the energy expended in physical activity.

This includes sports and exercise, but also taking the stairs, walking instead of riding the bus, even doing household work. Every bit helps for weight loss and also has other health benefits,[4] though dedicated exercise is easier to increase in expenditure and effect.[5]

But the beneficial effects of exercise are not only in the added expended energy. Doing exercise in addition to a reduced intake diet is much more effective than a diet alone.[6] And once the weight is down, exercise also helps keeping the fat off, one major problem for many dieters.[7][8]

On the other hand, exercise alone is not a very efficient way to lose weight.[9] A change of diet is needed. But even if no weight is lost by the exercise, the effects on health are significant.[10] Additionally, one of the more problematic side effects of losing weight with reduced intake is that the body is not only using fat mass for energy, but is also losing muscle mass. Even moderate exercises can help to attenuate this problematic effect.[11]

To sum this up, exercise is absolutely fantastic for you in every respect. And while normal activities count as a small form of exercise, it’s more beneficial to do it in a dedicated way. The following sections will give some numbers on how much exercise you should aim for, then give a quick summary of the two main exercise types, clear up some myths about sports, and finally try and give you a list of sports and exercises you can choose from.

It is absolutely paramount that you treat exercise not as some unwanted addition to your life that you do just to lose weight. Exercise is important for general health and once you have adopted a more active life style, you should aim to keep it that way forever. Make sports and exercise a hobby you do regularly, in addition to your other hobbies.


We are all human beings with other things to do than sports and exercise. While we should make some time for them, they shouldn’t dominate our life. For this reason alone, it is important not only to know what we should do, but when it is enough.

Losing 1,500–2,500 kcal per week to exercise—that is about 120 to 220 minutes of moderate-intensity exercise—have shown to be almost required to keep lost weight off.[4] Some studies even recommend that up to 275 minutes a week are very effective at keeping a low weight.[7] And indeed, the WHO recommends ideally about 300 minutes of moderate-intensity activity a week in “bouts of at least 10 minutes” each, and “muscle-strengthening activities involving major muscle groups on 2 or more days a week,”[12] while exercise in general should ideally happen on at least three, better four days of the week.[13]

If you are like me, you just got very unhappy. That sounds like a huge amount of time. And indeed, it will seem that way if you are not active so far. The main problem is that you have developed your day to day activities around an inactive life. You will need to adjust that a little and incorporate exercise and sports into your life. There is no way around that. Luckily, those numbers are the ideal, the goal, the maximum. You can grow slowly until you are comfortable there.

The WHO actually recommends at least 150 minutes of “moderate-intensity physical activity” per week (or 75 minutes of “vigorous-intensity activity”).[12] And even 80 minutes a week can be effective for weight loss already.[14]

Depending on your life style so far, pick a realistic first goal. Your major goal after about half a year should be the 150 minutes a week the WHO recommends as a minimum, but you can reach that amount in small steps.

As your first intermediate goal, for example, aim to hit 60 minutes per week for one month. Pick two days of the week and do 30 minutes of exercise on each. This could be a half an hour brisk walk after work on Mondays, and going home from work by bicycle on Fridays. If you can maintain this, you are doing well. In the second month, increase this to 90 minutes. Either add a third day, or extend one session to an hour. Third month, 120 minutes. At this point, I’d recommend joining a gym or similar health club. Once you are happy with the 120 minutes, extend it to 150 minutes. This could be, for example, two one-hour medium-intensity exercise sessions a week and half an hour of walking. And then you already have hit your first major goal. Be happy, you are doing more exercise than many others. Improve from this level only after you feel happy with it.

As for what to do in those times, the “moderate-intensity physical activity” that the WHO recommends includes household work and other common activities not normally associated with exercise, too.[15] That is, if you commit to half an hour of cleaning your home once a week, you already have done the “exercise” for one of the two days of the first month, and a much tidier home to boot.

The little stuff counts here, too. Use stairs whenever possible, walk the last bus stop home, park a bit further off and walk, take the bicycle to work. Anything you can think of that you enjoy.[4]

And I can only repeat. You need this time. Make the time in your normal schedule. Skip some TV, or wake up a bit earlier than normal, whichever works for you.

Strength and Endurance

There are basically two major kinds of sports that we are interested in.

Endurance training (or cardio) builds up stamina and lung volume, while burning quite a lot of calories in the process. Endurance training will also build up muscles to fight the muscle loss in diets,[11] but much less so than dedicated strength training would. Higher intensities of cardio training are generally more beneficial for health and stamina, but lower intensities do help just as much for fat loss.[16] This means that you can start slowly and have good effect from your training.

Strength training on the other hand is focused on building up muscles to fight against the loss of fat-free mass during weight loss.[17] It is also important to prevent various illnesses in the long term, and prevents aches such as a hurting back. It burns fewer calories per time than endurance training, but the increased muscle mass will burn more calories thorough the day. Even though that effect is not very large, every bit helps, and thus strength training does help quite a bit in weight loss.[18] Possibly surprising for newcomers is that the most effective strength training is done slowly.[19]

Sport Myths and Facts

For some reason, a lot of topics around weight loss are filled with myths and half-truths. Exercise and sports are no exception. The below will try to clear up some misconceptions.

Some of it will talk about improvements for weight or fat loss. Those are fine-tuning the process. Any exercise is much, much better than no exercise, and those little extras are only useful if they work well for you. Don’t go out of your way for them.

Exercise Before or After Food?

The question is, should we do exercise before we eat, or rather after? A lot of people recommend early morning exercise as particularly healthy. Is that so?

The answer is tricky. Studies have come to contradicting results.

Some have found that consuming carbohydrates before exercise actually reduces fat oxidation, which is optimal after six hours of fasting.[20] Especially exercise in the morning seems beneficial.[21] It is unclear if this leads to general better fat loss, as the body can convert fat to carbohydrates if those are low.

Other studies have found that to optimize losing body fat, exercise should happen after a light meal.[22] Also, exercising after a meal suppresses appetite more than fasted exercise,[23] which would speak in favor of exercise after food. Especially type 2 diabetes patients seem to benefit from that.[24]

Another point against morning exercise, especially before breakfast, is that eating directly after exercise benefits weight loss the most if the food is low on calories.[25]

All in all, I’d not worry too much about the timing. The effects are rather small, and exact recommendations are contradictory. Try not to exercise right after eating, as your body is preoccupied with digesting, but other than that, exercise when you can make it.

Does Fat Burning Only Start After 20-40 Minutes of Exercise?

I have no idea where this myth comes from, but simply realizing that the energy balance holds and that the body can convert energy reserves to whatever it is missing should tell you that it’s wrong.

And indeed, studies have found that separate, smaller lengths of exercise are at least as effective[26] if not more so[27] than singular, long exercise stretches. Even various intensities have shown no particular difference beyond the differences in calories expended, meaning a short higher-intensity exercise can perfectly well be replaced by a longer medium-intensity exercise.[28]

Even more so, shorter bouts of exercise seem to make it easier to follow the exercise plan.[27]

This makes me think that this myth was actually created by someone who wanted an excuse not to do short bouts of exercise whenever possible. “Oh, nah, I’m not walking the stairs, that doesn’t help anyhow, you know?”

The Fat Burning Zone

The infamous fat burning zone is highly contended on the net.

The basic idea is that there is apparently a level of exercise at which your body burns the most fat of the fuel sources it has available.[29][30] This happens at about 60% of your maximum heart rate, which is a bit under usual intensive exercise levels. And not only is training at that level good for fat loss, it is also beneficial for insulin resistance.[31] This is good news for new dieters, because it means you have an excuse to not train too intensively.

The bad news is that the differences in the fat loss range there are quite small, and that the variance of the maximum fat burning level is huge. In one test, it ranged from 41% to 91% of maximum heart rate.[32] Combined, this means that you don’t know where your maximum fat burning rate is, but that it doesn’t matter too much because the benefit of optimization is pretty slim to begin with.

Additionally, the energy balance holds true even here. If you burn more carbohydrates than fat, fat will be used to replace carbohydrate energy, too. If you burn more fat, carbohydrate will be used to replace fat. It does not matter that much which energy source you burn, as long as you burn energy.

There is a widespread counter-argument to the “fat burning zone” that claims that while percent amounts might prefer fat, absolute amounts do not. This argument is simply factually wrong. Figure 1a in [32] shows that the absolute amounts of fat go down, too. I have no idea why the net needs to invent false counter-arguments when perfectly good and correct ones exist, but there we go.

Obese People (BMI > 30) Should Not Be Jogging Or Running

This is a recurring claim, including from my doctor back then, but I have not been able to find the source for this. Quite to the contrary, it is being considered a myth and some health advice explicitly states that jogging is a good form of exercise even for the obese, provided of course that there is no prior joint damage or risk factor.[33]

The medical research on the topic is sparse. The best I found is that a large cross-sectional study has not been able to find a clear link between obesity, running and osteoarthritis in men, while obese females did show such a link.[34]

The main issue is that osteoarthritis has an increased risk for overweight and obese people,[35], and with such predisposition, exercise that puts a lot of pressure on joints are also problematic. Other than that, there seems to be no specific contraindication to jogging or running when obese. Do what you enjoy.

Start with brisk walking first, and improve to jogging and running only when you feel comfortable. If you have recurring pains, stop and go see a doctor.

Exercise Doesn't Help With Weight Loss Because It Makes Hungry

This is an argument brought up by low-carb evangelist Gary Taubes. While the intuitive reaction is what utter bollocks, intuitive reactions can be wrong in science, hence I did check scientific sources.

I found that “exercise did not change subsequent absolute energy intake, but produced a significant decrease (p < 0.05) in relative energy intake.”[36] Another study offered ad libitum food intake (i.e. at will, no artificial restriction) before and after exercise, and found that sixty minutes on the treadmill did lead to a negative daily energy balance and actually suppressed appetite.[23] And another study found “that large energy deficits induced by exercise do not lead to acute compensatory responses in appetite.”[37] The closest to the claim I found was that “although […] exercise trials […] produced an increase in appetite sensations, they did not alter energy intake and produced a decrease in […] energy intake.”[38]

So yes, exercise might increase appetite, but that doesn’t mean you eat more, and it still benefits weight loss. All in all, Gary Taubes’ argument sounds to me just like another excuse to avoid exercise. And a pretty poor one at that.

Sports to Choose From

So, now we know that exercise is great, that we can use everyday activity as exercise, and that it does not really matter all that much when or how intensive we exercise. But what can we actually do?

The important aspect for picking a sport is not how well it will help you lose fat, make you an athlete, or how efficient it is in anything. The main question is:

What kind of sport will you actually stick to?

Find sports that are close to you or on your way from work. The less effort you need to actually go there, the more likely you will stick with it. Having exercise equipment at home improves adherence even in scientific studies.[4] For the same reason, find something you enjoy, and do not feel bad about changing sports from time to time if you lose interest. The important thing is not what you do, but that you do something. There might be sports that are slightly more efficient, but that’s irrelevant if you simply don’t enjoy them.

Strength Training

Strength training is difficult to do without appropriate equipment. Still, it should be part of exercise plans for most people. The ideal solution here is to go to a gym and both get good equipment and professional supervision. This is not always a possible solution, though.

A cheaper alternative are bodyweight exercises, where the weight of your own body acts as the resistance to train muscles against, and can done at home with no or very little equipment. This typically includes push-ups, pull-ups and similar exercises. On-line lists of exercises are available from about.com, the Hacker’s Diet (a modified 5BX plan) or SimpleFit.

While the WHO recommends strength training on two to three days a week,[12] doing it on two days a week is only 20% less efficient,[39] so if that works better for you, great.

The rest of this list are endurance-focused sports.

Brisk Walking

An often overlooked type of exercise is the brisk walk. It can be done pretty much anywhere and with no special equipment. All of this makes it an ideal beginner’s sport.

As with most sports, the correct technique is important here. This might sound weird, as everyone is able to walk, but it’s impressive how many mistakes can be made there that ultimately reduce the health benefits.

Scheduling half an hour of walking to shut off after work or even during the lunch break is quite easy. At a good pace, it is possible to walk 2–3 km in half an hour.

Jogging, Running

The two words are used interchangeably, but people usually mean jogging with either.

Contrary to walking, some equipment (especially good shoes) is quite useful here, and as sweating is desired, it’s less easy to do this during the lunch break. Still, jogging can happen pretty much anywhere, so it’s an easy sport to get into.

The technique is even more important than with walking, as a bad technique can do serious harm to your joints.

Inline skating

Inline skating requires slightly more expensive equipment than jogging and better streets to be used nicely, but it’s a good variation and enjoyable to many.


Swimming is an excellent sport for obese people as the strain on joints is minimal and the exercise level is quite high. The equipment needed is not too expensive, but depending on where you live the entrance fees to swimming halls can be, and getting there might be annoying, reducing the likelihood of adhering to the exercise.


Cycling allows the combination of exercise with transportation, making it easier to incorporate into a busy life. The main drawback is that the equipment cost is rather high, especially for obese people who need a sturdier frame.

Elliptical Trainer

Probably the epitome of mechanized endurance training, the elliptical trainer and its variations of stationary cycle, treadmill, stepper etc. offer a wide variety of training options independent of the weather, the location, or other circumstances. Their main drawback is that they are quite expensive and that they don’t facilitate getting some fresh air.

If you have access to a gym, they usually also have some kind of cardio equipment available. Use it!


Exercise is good for you, for various reasons, including but certainly not limited to weight loss. Everyone, whether obese, overweight or normal weight should try and aim for good amounts of regular physical activity. Hence, exercise should become another hobby and part of your life, not just something you “have to do” that you want to get rid of eventually.

You should aim for at least 150 minutes of physical activity a week, but that includes household chores. Pick fixed days for dedicated exercise and slowly increase the time you spend on that. Both endurance and strength training are useful. And do not excuse yourself with lack of time—you need this activity.

While there are a lot of suggestions on how to fine-tune sports, actually doing something is immensely more important than the exact details. Every bit counts, every staircase you take, every minute you walk. But outside of the little things, there are a lot of good and fun sports to choose from as well. Pick one you like, do it until it’s not fun anymore, and then don’t feel bad about switching to something else. The only thing you should not be doing is to not do exercise.


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