I'm overweight and out of shape. I recently joined a gym to try and correct this. (Before you ask, yes, I asked my doctor about it. He said "Yes, please do, this is a good idea, have some brochures for local gyms, some of them have coupons.") I know that, for cardio, you're supposed to exercise for a minimum of 20 minutes to get any benefit. The thing is, I can't maintain 20 minutes at the intensity level the chart says is normal for my age. So, what's my best strategy for losing weight and getting healthier?

a) Exercise at full intensity, and gradually increase the time each day.

b) Exercise at reduced intensity for 20 minutes, and gradually increase the intensity each day.

c) Exercise at full intensity for less than (a), and then round out the 20 minutes with a less-intense exercise.

d) None of the above.

  • It’s important to define intensity here. Do you mean absolute or relative intensity? For example if we keep relative intensity the same, we should expect to see an increase in absolute intensity, that is, as fitness improves, you can go faster with the same level of effort.
    – Thomas Markov
    Commented Dec 3, 2022 at 22:54
  • @ThomasMarkov I looked the heart rate I "should" have on a couple of different websites, took an average, and try to match that. (I don't have a heart rate monitor, so I have to check my own pulse every now and then; if I'm high I slow down, and if I'm low I speed up.) Commented Dec 4, 2022 at 1:03
  • I know that, for cardio, you're supposed to exercise for a minimum of 20 minutes to get any benefit. I wouldn't be too sure about that, AFAICT this is an old sentiment without solid evidence behind it. For example, the 2020 physical activity guidelines from the WHO counts the total amount of aerobic physical activity, regardless of duration. The thing that really counts is the total volume (basically, duration multiplied by intensity), so you can reap equal benefit from longer workouts at lower intensity, or shorter workouts at greater intensity.
    – gustafc
    Commented Dec 5, 2022 at 12:21

3 Answers 3


(I am not a doctor so please ultimately consult and do your own research first.)

My Experience

When I first started training, I was skinny fat and my stamina/endurance was a total mess. I got into HIIT training apps that had mostly bodyweight exercises like the hellish burpee. It was very common for a workout to have many sets of burpees, and most of the times I couldn't keep up because my lungs were "burning" and my heart rate was pumping higher. This type of workout was brutal both physically and mentally, but it really helped me shed fat.

So how I kept going on?

I found that "finishing something" is most of the times more crucial than "giving it your all". And as a programmer, I can really see that fitting in other aspects of life (e.g. delivering a not-perfect but running code, than trying to produce a perfect code but not being able to deliver yet). I applied the same strategy with my workouts: Take my time but finish the whole thing.

What were the benefits?

  1. Increased Mental Capacity(1)

You had a X-intensity session and you finished it. Next time you will know better if you should try harder or go easier. This effect is going to multiply with each session, and you will have more and more a better understanding of what you should do.

  1. Increased Discipline(2)

It doesn't matter if it was hard or not, it doesn't matter if it lasted 10 or 30 minutes. What matters is that you went from point-A to point-B and this type of behavior will slowly turn it into a habit moving you one step closer to your goals.

  1. Gradual-Linear Progress

You did not get overweight in a day, so you will also not get fit in a day. Just like it took months or years for your body to adapt to an increased calorie intake, it will also take months or years to build the endurance to withstand a brutal session. However, with this approach, you give both to your body and mind the necessary time to recover and adapt.

Last but not least, do not blindly follow a guideline-chart and remember that deciding to work out is on its own a progress. Just show up each day and put the best work you can put. Rome wasn't built in a day.


The main question you want to ask yourself when approaching any training programme (which is what you are describing by incremental increases in your training stimulus) is, what is/are my fitness goal(s)?

Your goals

From what you described above, there are two potential goals that I can infer from your question:

Goal 1.) From the following statement:

"I can't maintain 20 minutes at the intensity level the chart says is normal for my age"

I infer that you want to increase your anaerobic endurance with a specific goal of 20 minutes continuous exercise at high-intensity.

Goal 2.) From the following question you posed:

"What's my best strategy for losing weight and getting healthier?"

I infer that you want to improve your body composition i.e. decreased body fat percentage.

Addressing those goals

So with these two goals in mind, typical routines a personal trainer (PT) may prescribe for you to address those goals are:

Goal 1a.) Tempo training -> Operating at a high intensity continuously (maintaining 80-90% maximum heart rate or 'finding it hard to say more than a few words') for up to ~20 minutes. Typically, after an initial fitness assessment the PT will know how long you would be able to maintain that heart rate zone. Week on week, your time would then be increased until you have reached your 20 minute goal at the intensity level mentioned before.


Goal 1b.) High-intensity interval training -> Operating at high intensity for short periods, followed immediately by rest periods, and then repeated continuously. Typical work to rest ratios range between 1:2 and 1:6 with some studies finding the optimal WTR ratio being 1:4 (Myong-Won et al 2019). This means, for a WTR ratio of 1:2 you may work for 30s and rest for 60s. Generally, during your working period you want to be operating fairly maximally (~95%). A PT will typically increase the number of sets per week until you can easily handle the exercise prescribed. At this point they will then make the work period 'harder' and dial back the sets. Rinse and repeat.

Goal 2.) Although improvements in body composition can come from increasing your muscle mass through a dedicated weight training programme, I will only concentrate on losing fat as a way of improving your body composition/general health. This is fairly simple. You have to operate on a calorie deficit i.e. the amount of calories going in through food has to be less than the amount of calories going out from general life and exercise. How to do this? Well the training programme will pretty much take care of the increase in calories going out. A PT would also suggest a meal plan so they can track the number of calories going in. If you need 2000 kcal per day, the meal plan will likely incorporate food totalling less than that. The exact number depends on what calorie deficit you want to impose e.g. a calorie deficit of 200 kcal means you will eat 1800 kcal a day. In my experience, large calorie deficits are not maintainable in the long term since they are not enjoyable in the least. A calorie deficit ~200 kcal works well if the client is happy to wait a little longer to shed the pounds, because consistency wins every time.

The Takeaway

As you can see above, you simply asked about what is better, increasing the time, or increasing the intensity? However, you also have to think about what you want to achieve. Just considering the choice above misses out on key factors, which need to be considered to achieve the goals you outlined.

In summary, to address the goals within your question:

  • Maintain the same intensity across exercise sessions, but increase the time exercising until you have reached your 20 minute goal. This can be achieved through either tempo training or HIIT considering the intensity and time you mentioned. After achieving your goal of 20 minutes at a desired intensity, you can think about creating a new goal focussing on increasing this.
  • Operate at a calorie deficit through exercise and consideration of your diet in order to lose weight and increase your general health.

PS - As mentioned in a comment above, the 'I must exercise more than 20 minutes to see any benefit' is a myth and completely false. To see benefits, stick with consistency and increasing your training stimulus over time.


Depending on your current situation, the best strategy for losing weight and getting healthier may be to choose b) exercise at a reduced intensity for 20 minutes, then gradually increase the intensity each day.

Starting at a lower intensity will allow you to exercise within your current fitness level and avoid overexertion or potential injury. As you continue, you can gradually increase the intensity as your fitness improves. This approach helps build endurance and allows your body to more safely adapt to your new exercise routine.

When it comes to working out, I find my BP Doctor smartwatch helps me a lot. It keeps track of my workouts and body conditions, allowing me to analyze and make adjustments in real time.

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