Tuesday, February 14, 2012

HIT the Cravings - Eat Less, Improve Your Health & Lose Weight: "Burning 350kcal" at >75% VO2-Max Improves Calorie Balance Doing it at 40% Just Makes You Hungry!

Image 1: Even if the boys in the study at hand still ate "more calories than they expended", HIT would certainly slow their progress from the healthy kid in the left to the obese and more importantly unhealthy one on the right.
Have you ever wondered why the Biggest Losers do survive their almost zero calorie diets? Well, a recent study from the France could well hold the answer (Thivel. 2012): Their intense and often temporarily totally exhausting exercise regimen! "What? That insane cardio + whatever you may call that torture 12h/day ..." - I see you are surprised, because in essence most of the stuff they do appears to (and actually is) totally idiotic. I am however not growing tired of repeating that even taking the stairs easily turns into an high intensity exercise if you have to carry a 200lbs apron of fat from the ground- to say the third floor. If you don't believe it, do 50 lunges with 200lbs and tell me that this ain't "high intensity" ;-)

HIIT holds the key to health and satiety... and that is probably why it facilitates weight loss!

When I think about it, for a morbidly obese person, taking the stairs could in fact be even more intense than the 75% VO2Max high-intensity cycling protocol the 15 obese boys (age 13.5y; BMI: 30.7; waist: 104.3cm; fat mass 38.2%) from the Pediatric Obesity Department of the Children’s Medical Center of Romagnat (France) performed at roughly 3h after ingesting a standardized breakfast, the caloric content of which was matched to the calculated energy expenditure, i.e. rest + exercise-induced (the boys had to cycle until they had performed a workload equivalent to ~350kcal) of the entire morning in order to isolate the effect of exercise intensity from that of energy status on subsequent energy intakes at launch and dinner, as well as macronutrient pereferences, energy expenditure and appetite sensation, which were the other dependent variables, David Thiel and his colleagues recorded after the aforementioned high intensitiy and separate (7-days washout) low intensity (40% VOMax, again 350kcal) exercise and sedentary control conditions.
Figure 1: Energy intake, expenditure and balance of the boys in the three test sessions (calculated based on
If, for the time being, we disregard the beneficial health effect any type of physical activity will have over just sitting around pondering which of those foods in front of you contain "good" and which contain "bad" calories, the (statistically non-significantly) increased "energy balance" in the low intensity exercise condition (cf. figure 1) does in fact confirm Dr. Oz' somewhat skewed summary of Garry Taubes' statement that exercise would "just make you hungry". The statistically significant reduction in energy intake (-6%, p<0.05) and the even more profound decrease (-25%, p<0.01) of the 24h "energy balance" in the high intensity exercise condition, on the other hand, support the (fortunately) evermore popular notion that short and intense exercise sessions, not daily marathons in the "fat burning" zone, are the ideal complement to any dietary intervention that is targeted at loosing weight and improving metabolic and overall health (suggested read: Previous news on HIT / HIIT)
A brief note on the notion of  "dietary interventions": For15 year old boys who habitually consume >3500kcal/day any "dietary intervention" to prevent them from morbid obesity, diabetes and all the other ailments by which large parts of the Western society is plagued, must inevitably include a reduced calorie intake! While the importance of the daily "energy balance" is certainly overblown and any holistic diet + exercise + lifestyle intervention should be designed to induce a natural, satiety-induced reduction in energy intake by combining a reasonable amount of intense exercise with a nutrient-dense diet like, but not necessarily identical to a low-, but - in most cases - better not no-carb "Paleo Diet", complete ignorance towards the amount of food you consume will inevitably compromise your results - no matter how "good" the calories you are consuming may be.
In this context, it is also noteworthy that the reduction in calorie intake in the HIT trial was more pronounced at dinner than at launch and that the non existent differences between the ratings of subjective hunger, fullness or prospective food consumption in the three experimental sessions, cannot be accounted for by changes in the macronutrient composition of the subsequent ad-libitum meals, which were equally "identical" (within statistical margins, obviously) for the high intensity, low intensity and sedentary control session.

Hard and short = full and happy - what more can you ask for?

Image 2: I guess if parents were better role-models and encouraged their children to exercise (with them), childhood obesity would not be such a huge problem, anyways.
If you look for the underlying reason for the voluntarily reduced energy intake in the high intensity exercise condition of the study at hand, the results of another recently published paper by Balaguera-Cortes et al. comes to mind (Balaguera-Cortes. 2012), in which 10 "active" men completed 45min of either aerobic or resistance training in a similar counter-balanced fashion. When the scientists measured the exercise-induced hormonal changes, they found significantly lower levels of the "hunger hormon" ghrelin in the resistance compared to the aerobic exercise condition. Interestingly, though, the energy intake of these normal weight subject at a subsequently provided breakfast buffet was identical in both conditions.

While the very different exercise stimuli of HIT (Thiel study) and HIIT, on the one hand, and resistance training (Belaguera-Cortes study), on the other hand, could account for the differential effects on subsequent energy intake and would thusly support the notion that resistance training alone is not sufficient to induce significant reductions in body weight.  

I feel that further research is needed to establish, the influence of being obese or lean and/or being used to overeat vs. eating at maintenance exerts on the resistance exercise-induced increase in energy intake and the long-term effects of the latter not on body weight, but body composition.