Energy Balance and Everyday Activity Explain Weight Loss Success / Failure W/ Exercise in Men, But Not in Women

Bicycling to work is one of these "small things" that may make the difference between lean and obese.
I know this is not what your friends will want to hear, but for 99.9% of them it's not their genes which are to blame for their inability to lose weight. It's much simpler than that: It's their inability or unwillingness to induce a large enough caloric deficit to force their bodies to tap into the fat stores. Don't get me wrong: It's obvious that genes, with their direct and indirect influence on one's basal energy requirements (think of being tall vs. being small, if nothing else), amount of muscle, and even ability to handle glucose and fats, will factor in here. In the end, however, it's everyone's knowledge about the dos and don'ts of dieting, effort and dietary adherence that will make the difference.

That's no news for you? I think the results of a recent study from the University of Kansas Medical Center and the Texas Tech University will still come as a surprise. Usually, we talk about cheating on one's diet, skipping scheduled workouts and eating foods people are not supposed to eat, when we discuss the reasons why people fail. The results of said study, however, suggest that something else may have a much larger impact: Our regular non-exercise physical activity.
No "metabolic damage" here, but here are posts that relate do increased / decreased REE

Orgasm Hormone Increases REE

9 Tricks to Keep You REE Up

High EAA Intake, High REE

You're not a Bomb Calorimeter

Calorie Shifting for Max. Fat Loss

Met. Damage in Big Losers?
If you've read my March 2015 article "It Doesn't Have to be an Exhaustive Workout - Increasing Physical Activity Just as Effective as Strength, Endurance or Combined Exercise to Lose Fat and Build Muscle" (read it now), you will know about the importance of "taking the stairs", standing instead of seating, bicycling to work and other often overlooked low-intensity non-exercise physical activity in our everyday lives. Interestingly enough, it is just this type of low intensity 'non-exercise' of which the so-called "Midwest Exercise Trial 2" indicates that it is what distinguishes the weight loss responders (>5% weight loss) from the non-responders (<5% weight loss) in a relatively tightly controlled "work out five times per week for 10 months to lose weight"-intervention by Herrmann et al. (2015).

Before we are dealing with this surprising result, though, let's first take a look at what exactly the N=141 18-30 year-old men overweight/obesity (BMI 25-40 kg/m²) subjects had to do in this 'exercise for weight loss study' (details can be found in the description the scientists published when they registered their clinical trial | Donelly. 2012):
  • Table 1: It is important to note that there were no sign. baseline differences in weight, age, etc. between responders and non-responders among the study participants (Herrmann. 2015).
    the subjects exercised on 5 days of the week - one of the session was "choose the activity you want", the other sessions were performed under supervision walking/jogging on treadmill
  • the duration / intensity of all workouts was matched to initially burn 150 kcal; from months for on, 400 and 600 kcal/session (this is in line with the "2008 Physical Activity Guidelines for Americans" | USDA. 2008) 

I see you're looking for the dietary advise? Well, there was none. That may look awkward, but in view of the fact that the scientists wanted to see whether the simple adherence to the USDA "Physical Activity Guidelines for Americans" would make a difference, the subjects were told to stay on their regular (junk food?) diets.
A friendly reminder for the trainers out there: While it may be enough to increase your clients activity level, long-term weight loss can be facilitated only if you attack all weight- and health-relevant aspects of a clients life-style. That's (I) exercise and everyday activity, (II) diet and (III) sleep (circadian rhythm), stress and related aspects of their lifestyle.
As the name of the study or rather the index "2" in the name implies, the "Midwest Exercise Trial 2" is a follow up study. It's a follow up that was supposed to elucidate (a) what distinguishes responders from non-responders and whether (b) the gender differences in weight response Donelly et al. observed in their 2003 predecessor study were coincidental or something we have to keep in mind, whenever we are designing exercise-based weight loss routines for men and women..
Figure 1: Total daily energy expenditure (TDEE), nonexercise energy expenditure (NEEx), and resting metabolic rate (RMR) at baseline and 10 months in responders (RS) and nonresponders (NR) to an aerobic exercise intervention.
What should I say? If you look at the data it would almost seem as if (2) was the case: Men and women appear to respond very differently to this kind of exercise-based weight loss efforts. Yes, the data in Figure 1 shows that there is a trend for non-responders from both sexes to be less active in their free time and thus having a lower non-exercise induced energy expenditure (NEEEx). On the other hand, though, ...
  1. Figure 2: Nonexercise physical activity (NEPA) and sedentary time across 10 months in responders (RS) and nonresponders (NR) to an aerobic exercise intervention (Herrmann. 2015).
    only the male non-responders are truly characterized by their tendency to take the five weekly workouts as an excuse to use the elevator and drive the 200m to the next fast-food outlet by car, while 
  2. there is no such compensatory effect on NEEEx in the women and even an increase in resting metabolic rate (so no metabolic damage or shut-down) in the female non-responders
This trend for a "compensatory effect" on non-exercise physical activity (NEPA) in male and its absence is in female non-responders becomes even more obvious in Figure 2.
Figure 3: Rel. energy balance in male and female weight loss responders and non-responders in month 10 - data calculated as (total intake / total expenditure - 1)*100 based on data from Herrmann et al. (2015).
If we go back to my initial comment on caloric deficits and do the math that's required to calculate the relative difference between the total reported energy intake and the estimated energy expenditure, we get an excellent explanation for the fact that the male "non-responders" don't lose weight: They simply weren't in caloric deficit (see Figure 3); and that - and this is actually the most interesting finding - not because they ate more (the reported energy intake didn't change much), but because they moved less in their everyday lives!
I don't want to point with a finger to the non-responders, but energy intake underreporting is an issue you cannot ignore with overweight young(er) women (data from Smith. 1994).
So, what to we do with the women? Is there something that makes women resistant to exercise induced weight loss? I am not sure if it is politically to discuss this, but previous studies actually confirm the obvious: Women tend to lie about their food intake, more frequently than men. Particularly in overweight women underreporting (consciously or not - I don't care) is highly prevalent (Klesges. 1995; Smith. 1994). Especially the highly obesogenic snacks people and caloric beverages tend to "inhale" in-between their meals are often "forgotten" (Poppitt. 1998). Next to an overall tendency to underreport their overall energy intake, obese individuals have also been found more likely to overreport their protein intake and "forget" about fats and sugars, in particular (Heitmann. 1995), ... but let's focus on this study.

With the estimated number of calories that are "forgotten" being estimated around ~17% in all women (sign. higher in obese women), the sex difference may have a methodological, not a physical cause. The only problem here is that all women were overweight or obese. We do thus have to assume that the "responders" were underreporting their food intake, as well. So, if the female non-responders don't compensate on either the physical activity or the diet-side of things and the increasing resting energy expenditures of the non-responders (which would by the way still indicate they ate more than they said) excludes that they had a tough time due to being genetically disadvantaged by "having a slow metabolism" or "a thrifty phenotype", further research is necessary to elucidate what exactly it is that makes some women fail, where others succeed.

Luckily we don't need the answer to this question to state at least one very important conclusion: Diet interventions that are targeted towards exercise induced increases in energy expenditure are better suited for men - in particular for those men who are willing to actually increase their overall activity level, instead of compensating for the time they spend working out in the gym, on the track or wherever else by increasing their "couch time" | Comment on Facebook!
  • Donnelly, Joseph E., et al. "Effects of a 16-month randomized controlled exercise trial on body weight and composition in young, overweight men and women: the Midwest Exercise Trial." Archives of Internal Medicine 163.11 (2003): 1343-1350.
  • Donnelly, Joseph E., et al. "A randomized, controlled, supervised, exercise trial in young overweight men and women: the Midwest Exercise Trial II (MET2)." Contemporary clinical trials 33.4 (2012): 804-810.
  • Herrmann, Stephen D., et al. "Energy intake, nonexercise physical activity, and weight loss in responders and nonresponders: The Midwest Exercise Trial 2." Obesity 23.8 (2015): 1539-1549.
  • Klesges, Robert C., Linda H. Eck, and JoAnne W. Ray. "Who underreports dietary intake in a dietary recall? Evidence from the Second National Health and Nutrition Examination Survey." Journal of consulting and clinical psychology 63.3 (1995): 438.
  • USDA, Physical Activity Guidelines Advisory Committee. "Physical activity guidelines for Americans." Washington, DC: US Department of Health and Human Services (2008): 15-34.
  • Poppitt, S. D., et al. "Assessment of selective under-reporting of food intake by both obese and non-obese women in a metabolic facility." International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity 22.4 (1998): 303-311.
  • Smith, Wayne T., Karen L. Webb, and Peter F. Heywood. "The implications of underreporting in dietary studies." Australian journal of public health 18.3 (1994): 311-314.
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