Exercise for Weight Loss (the TRUTH)

Hello,

Exercise! Every time I say "weight loss", I hear "exercise". Mostly because everyone around me thinks that they should advise whoever wants to lose weight to start exercising.  Intuitively, it sounds like a good advice, but after years of training and studying human body, I beg to differ - I believe that exercise has a very limited effectiveness for weight loss and, in many cases, it is counterproductive if not harmful.

In this blog, I'm going to give you the truth about exercise for weight loss based on my knowledge and I'll support it with some good research evidence. Feel free to check the Science section for extra information.

Let's start with the statement that seems to be right intuitively - obviously, exercise in general has a number of positive effects on our bodies. The main argument for using exercise to lose weight is that we spend energy to perform movements and, thus, exercising shifts our energy balance in the direction of weight loss. Then we also burn more calories to recover from the exercise in the next day or two and, in addition to that, building some muscle increases our metabolic rate by adding very metabolically active tissue mass.

All these effects are undeniably true, but do they really help us to lose weight? Let's take yours truly as an example. Currently, I weigh around 85 kg (just a bit less than 190 lb) and my Basal Metabolic Rate (BMR) is around 1,900 kCal/day. My Total Daily Energy Expenditure (TDEE) is somewhere in between 2,300 and 3,000 kCal/day. Let's assume it's 2,500 kCal/day. Say, I decide to lose weight and start working out 3 times a week, realistically, with moderate intensity for 45 min each time. If we just check some calculators to see how much energy I spend we can see that I should spend around 0.05 kCal/min/lb (the number is for vigorous strength training) or 423 kCal per workout. Or, for example, if I decide to run or jog, say, do some moderate-speed running, like 10 mph and I would run 5 miles (30 min) - we get 621 kCal per 1 session (which, I know for sure an overweight person can't start doing right away, but it's a hypothetical scenario). Let's also assume that my muscle recovery between resistance training sessions is the same as my energy expenditure during the actual workouts (no one really knows the exact amount) and though my endurance exercise does not produce that much of an effect in terms of muscle building, we will assume that whichever training I choose, I would burn on average around 500-600 additional kCal per day. That looks like a massive 15-20% metabolic boost! And it truly is!

The problem with that is that in majority of cases increasing energy expenditure doesn't really create a caloric deficit - these 500-600 kCal per day are easily negated by a single sandwich! I'll use McDonald's Big Mac as an example (563 kCal). I have nothing against McDonald's - they are just super convenient to use as an etalon of caloric intake as they are the same all over the world. As a side note, let's consider using our own Big Mac Index (1 Big Mac = 563 kCal) for nutritional calculations!

Anyhow, my point is - when people spend more energy they still have to go on a diet to restrict their caloric intake. Otherwise, they are not creating any actual caloric deficit and do not lose any weight. In fact, they might even gain weight due to increased appetite and caloric intake.

Couple of other claims on the list:

1. Exercise builds muscle and muscles burn more energy at rest:
   Yes, this claim is true, but let's look at how much muscle you can build and how much energy muscle burns at rest. An average person can only build several kilograms (maybe 10 pounds or so) of muscle mass in the first year. This is quite a controversial number as estimates vary  greatly, but I think it would be safe to say that if you start a good program, you will only gain several pounds of lean muscle in the first several months. According to well-established research data1, human muscle's resting energy expenditure is just 13 kCal/kg/day, or 6 kCal per pound per day! So, even if you gain 15 pounds of lean muscle mass, you will still spend less than 100 extra calories per day. I think it's negligible and shouldn't even be considered as a weight loss item. Also, let's not forget, that in order to increase your BMR by 100 kCal you'd have to gain 15 lb of body weight.
   
2. Exercise has a number of other health benefits:
   Again, I agree wholeheartedly - it does when used properly and I would advocate for the incorporation of exercise in any weight loss program, but gradually and taking into consideration a number of individual factors such as fitness level, body mass, pre-existing health problems etc. The reason why I mention this is simple - if you are seriously overweight, you cannot perform a lot of exercises without deleterious effects on your health. The very first exercise that crosses my mind (as virtually everyone recommends it) is jogging - if you are overweight you will likely overload your cardiovascular system and you will definitely damage your joints, at least your knees. Add to this the fact that you won't be able to run with high intensity and for a period of time long enough to burn any substantial number of calories. My suggestion is - don't engage in exercise unless and until you can do it safely and to your benefit.
   

So, let's summarize - if you engage in exercise you are spending time and effort to increase your metabolic rate. The increase of metabolic rate is easily offset by having an extra snack, the resting metabolic rate increase is negligible and whatever potential health benefits you might get from exercise are outweighed by the almost guaranteed damage to your cardiovascular and musculoskeletal system. Does exercise still look like such a great tool for weight loss? If you're not convinced yet, I'd like you to see some actual research.

Here is an excellent meta-analysis by Dr. James E. Clark2 published in the Journal of Diabetes & Metabolic Disorders in 2015. The meta-analysis summarizes 66 population-based studies and includes 162-studywise groups (with thousands of subjects included overall).

You are more than welcome to examine this article yourself in the Science section, but the main take-home points are as follows. Please note that we use effect sizes (ES) as a standard measure of the impact of the approach:

1. Caloric deficit is essential for weight loss - the total body mass changes were most pronounced in the diet only group (ES*=1.24)
   
2. Endurance training alone did not produce any significant changes in body mass
   
3. Resistance training alone produced minimal changes in body mass (ES=0.25)
   
4. Addition of exercise to the diet resulted in less intense weight loss with effect sizes of 1.19, 1.06 and 0.57 for endurance training, resistance training and both types of exercise added to the diet, respectively.
   
5. At the same time the addition of exercise, especially resistance training helped to spare lean body mass and had a number of other positive metabolic and hormonal benefits.
   

I guess, it's time for me to say "I rest my case" and to repeat my core recommendations to incorporate exercise wisely - do so only if you see the benefit of it in your program and when you can do it without negative health effects.

Sincerely Yours,

Dr.Sam

Video: Exercise For Weight Loss (The TRUTH)

1. Wang Z, Ying Z, Bosy-Westphal A, et al. Evaluation of Specific Metabolic Rates of Major Organs and Tissues: Comparison Between Men and Women. American Journal of Human Biology. 2011;23(3):333-338.

2. Clark JE. Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18-65 years old) who are overfat, or obese; systematic review and meta-analysis. Journal of Diabetes & Metabolic Disorders. 2015;14(1):31.