Why it can sometimes pay to be realistic about the impact of exercise on weight loss

January is not that far away now and when it comes around at least some people will turn their thoughts to shedding surplus pounds through diet, exercise or both. I came across a report this week of a recently-published study which compared the effects of aerobic exercise with resistance training on weight and fat loss. The report stated that aerobic exercise was the clear winner, but neglected to give any actual amounts of weight lost. I have to admit I was a little suspicious because previous evidence has shown that aerobic exercise has limited effect on weight, generally speaking. I went to find the actual paper [1] to see if the devil was in the detail.

In this study, sedentary overweight and obese adults were randomised to one of three exercise groups for a period of 8 months.

  1. aerobic exercise (treadmill, cross trainer machine, stationary bicycle) for a total of 12 miles a week at 65-80 per cent maximal intensity.
  2. resistance training on 3 days per week designed to burn the same number of calories as the aerobic exercise of group 1.
  3. both aerobic exercise and resistance training combined (group 1 exercise plus group 2 exercise)

The results revealed that both groups 1 and 3 lost weight and fat, and group 3 lost no more weight and fat than group 1 (despite doing twice as much exercise). Group 2 did not lose weight. All this led the authors to conclude that aerobic exercise is superior for weight loss. But what I (and perhaps other people) really want to know is just how effective the aerobic exercise was in terms of weight loss.

It turns out that individuals in group 1 lost a total of 1.66 kg (about 3.5 lbs) of fat. Remember, though, this is over an 8-month period, so the pounds were not exactly dropping off. Now, let’s factor in the amount of exercise the amount of exercise required to achieve this weight loss result…

Individuals exercised for a total of about 2 hours a week which means that the total amount of exercise over the study period came to about 70 hours. For each hour of exercise individuals lost about 1 ounce (or about 30 grams) in weight.

Let me be clear and say I am not writing this to dissuade individuals from taking exercise and being active. I am an enthusiastic advocate of physical activity, and believe it has the capacity to benefit health in many ways. However, my experience tells me that many people use exercise to regulate weight and that this is particularly the case in January. I also know that many are disappointed with the results they achieve, feel something is ‘wrong’ with them, and can give up altogether when they don’t feel they’re getting a return on investment.

I think it helps some to know that substantial weight loss is unlikely to come from exercise, so that expectations are aligned with the likely results. Then, individuals may not be so disappointed when they don’t get the ‘expected’ results from exercise with regard to weight loss.

So, I encourage individuals to exercise if they can, but to focus on benefits they are likely to experience such as improved physical and psychological wellbeing and improved fitness.

It occurs to me that this latest study may cause some to conclude that there’s not much point to resistance exercise. Actually, I think there is. It can strengthen the body, which can improve mobility and reduce frailty, which is particularly important for the elderly. It also can improve the aesthetics of the body, which some are grateful for.

Being realistic about the likely impact of exercise on body weight and focusing on whatever else it has to offer can, I think, help motivate us to be active and stay active.


1. Slentz A, et al. Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults J Appl Physiol 2012;113:1831-1837

14 Responses to Why it can sometimes pay to be realistic about the impact of exercise on weight loss

  1. garymar 21 December 2012 at 2:15 pm #

    It looks like the Aerobic + Resistance training group got the best of both worlds: fat loss AND muscle increase, and as much waist reduction as the Aerobics alone. But they had to double their time commitment to exercise. The conclusion seems pretty firm that for overweight, sedentary individuals, the biggest bang for the buck comes with Aerobics alone — the minimalist program, as it were.

    Me, personally, I use RT more because of much less stress on the joints, and the resulting strength that promotes greater facility in everyday living (but then I’m not overweight). And anyway you can’t out-exercise a bad diet.

  2. Kris Gunnars 21 December 2012 at 3:43 pm #

    I would like to have seen numbers on body composition. Groups 2 and 3, who did lift weights, are likely to have gained some lean mass while losing fat. This wouldn’t show up on the scale, but would need a high accuracy body fat measurement like DEXA.

    But I agree, exercise alone for weight loss is very ineffective. Personally though I find that I tend to eat healthier if I exercise, cravings seem to be less for some reason and it becomes easier to make healthy choices.

  3. DeWayne 21 December 2012 at 8:18 pm #

    Spot on. I lost 60 lbs through diet, I then started an exercise program hoping to lose an additional 10 lbs or so. I never budged off my current weight. I still exercise , but for the other benefits.

  4. Michael Barker 21 December 2012 at 9:56 pm #

    My question is how much muscle did the 2 group put on?

  5. Gerda Flöckinger C B E 21 December 2012 at 9:57 pm #

    I wonder whether anyone on this blog has ever watched ‘Strictly come dancing’. I’m mostly amazed by just how much weight the fatties – as long as they stay in the contest for long enough – have lost after some weeks of hard ballroom dancing, most of them without having bothered to change their diets at all. Pamela Stevenson lost at least two stone over the period, and in the current series there have also been amazing weight losses. With one of the women it’s been very interesting to see the three chins reducing to just the one, and a human body gradually emerging from the layers of fat she started with just a few weeks ago.

  6. chuck 21 December 2012 at 10:24 pm #

    i wonder if you have full access to the paper as I don’t. I am curious about actual body fat lost in groups 1 and 2. I’d also like to know about changes in lean body mass in groups 1 and 2.

  7. Ann 22 December 2012 at 12:34 am #

    GERDA – my understanding about those dance competition shows is that all those people are doing most of the day, most days, is practicing routines. It becomes their jobs, if you will. They are losing weight because of the sheer caloric deficit they are creating by exerting themselves for so many consecutive hours. Over here in US we have a show called “The Biggest Loser” and it is very much the same. Success is virtually guaranteed for those contestants because they have coaches (watchdogs), chefs, and personal trainers keeping them on track all day. Add to that the six or so hours per day of exercise they endure, and naturally they lose weight. However much they lose, and however many health benefits they may gain from the experience, that kind of situation nearly always sets them up for failure and a return of the lost pounds when all those previous supports are removed and the contestant returns to “normal” life.

    It really doesn’t paint a very practical picture for the rest of us with regard to using exercise to lose weight and keep it off. I don’t know anyone who has that many hours a day to devote to exercise for the rest of their lives. Professional athletes maybe, who are earning a living from their athletic performance, but most of us have jobs and lives.

    I think it is also true to note as well that what a person does to lose a significant amount of weight, be it exercise or dietary modification, that must remain the lifestyle if one is to keep the weight off. What you do to lose the weight, you must continue doing to maintain the weight loss. It pays to find a way that is sustainable.

  8. PhilT 22 December 2012 at 1:17 am #

    “and group 3 lost no more weight and fat than group 3” – shome mishtake, shurely ?

  9. Dr John Briffa 22 December 2012 at 1:22 am #

    Thanks PhilT, corrected now.

  10. PhilT 22 December 2012 at 10:40 am #

    @chuck http://jap.physiology.org/content/113/12/1831.long

    Group 1 gained 1.05 kg of lean mass, groups 2 & 3 change not significant. Groups 2&3 lost 1.66 and 2.44 kg of fat respectively, group 1 not significant.

  11. Docsopinion 22 December 2012 at 10:29 pm #

    I think that isolating the the effects of exercise on weight loss from other health benefits may be a bit misleading. In my mind, regular exercise is an important part of every weight loss program, due to the effects on general health, metabolism, muscle strength, insulin resistance, general and visceral obesity. Body mass index does not tell it all.
    A recent study published in JAMA has indeed shown positive effects of regular exercise on obesity in children although BMI may not have been affected much. http://www.ncbi.nlm.nih.gov/pubmed/22990269

  12. garymar 23 December 2012 at 2:15 am #

    Everybody, look at Figure 2 and Table 2.
    RT group gained 1.09 kg lean mass, statistically significant.
    RT+AT group gained 0.81 kg lean mass, statistically significant. (AT group change not significant.)

    Plus the RT+AT group lost waist circumference (significant) and fat (significant). Like I said, best of both worlds! Go for a walk and lift weights (which is what I did yesterday).

  13. Chloe 30 December 2012 at 9:36 pm #

    More confusion…I can’t take it!!!

    I would recommend the benefits of lifting really heavy stuff for your confidence however. I like showing the men in the gym how it’s done! Leave feeling like I can take on the world!

    Dr B, why have you disappeared from Twitter 🙁

  14. Jonathan Bagley 7 January 2013 at 11:22 pm #

    I’ve been doing 3. for about 18 months now, plus eating more protein, less sugar and slightly less bread. Still drink a fair amount of alcohol. My weight has stayed the same, but I’ve lost around 2″ from my waist. I’ve definitely gained quite a bit of muscle.

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