Severe negative energy balance during 21 d at high altitude decreases fat‐free mass regardless of dietary protein intake: a randomized controlled trial

Abstract

In this 2-phase randomized controlled study, we examined whether consuming a higher-protein (HP) diet would attenuate fat-free mass (FFM) loss during energy deficit (ED) at high altitude (HA) in 17 healthy males (mean 6 SD: 23 6 6 yr; 82 6 14 kg). During phase 1 at sea level (SL, 55 m), participants consumed a eucaloric diet providing standard protein (SP; 1.0 g protein/kg,) for 21 d. During phase 2, participants resided at HA (4300 m) for 22 d and were randomly assigned to either an SP or HP (2.0 g protein/kg) diet designed to elicit a 40% ED. Body composition, substrate oxidation, and postabsorptive whole-body protein kinetics were measured. Participants were weight stable during SL and lost 7.9 6 1.9 kg (P < 0.01) during HA, regardless of dietary protein intake. Decrements in wholebody FFM (3.6 6 2.4 kg) and fat mass (3.6 6 1.3 kg) were not different between SP and HP. HP oxidized 0.95 6 0.32 g protein/kg per day more than SP and whole-body net protein balance was more negative for HP than for SP (P < 0.01). Based on changes in body energy stores, the overall ED was 70% (21849 6 511 kcal/d, no group differences). Consuming an HP diet did not protect FFM during severe ED at HA.-Berryman, C. E., Young, A. J., Karl, J. P., Kenefick, R. W., Margolis, L. M., Cole, R. E., Carbone, J. W., Lieberman, H. R., Kim, I.-Y., Ferrando, A. A., Pasiakos, S. M. Severe negative energy balance during 21 d at high altitude decreases fat-free mass regardless of dietary protein intake: a randomized controlled trial. FASEB J. 32, 894-905 (2018 For lowlanders sojourning at high altitude (HA .1500 m), maintaining energy balance can be challenging because of an increase in resting metabolic rate (RMR) (1, 2) and a decrease in appetite (3) caused by physiologic adaptations to hypoxia. The effects of hypoxia on energy balance are frequently compounded by limited access to food and high physical activity levels while at HA. Negative energy balance usually develops at HA and typically leads to weight loss (4). Barnholt et al. (4) showed that individuals sustaining a 40% energy deficit (ED) for 21 d at HA lost more body weight than individuals adhering to the same controlled diet and physical activity at sea level (SL). Furthermore, some studies (5-8) have observed .50% of total body mass (TBM) loss as fat-free mass (FFM) during prolonged ED at HA, which is greater than the 25-35% typically observed at SL (9-11), suggesting protein turnover kinetics and substrate utilization during weight loss at HA may differ from that at SL.At SL, protein intake above the Recommended Dietary Allowance (RDA, 0.8 g protein/kg per day) limits FFM loss during moderate negative energy balance (;40% ED) in healthy, normal weight adults (12)(13)(14). We have shown that consuming a diet containing 1.6 or 2.4 g protein/kg per day (2 and 3 times the RDA, respectively) for 21 d, within the context of a 40% ED, attenuates FFM loss as a percentage of TBM loss (30 6 7 and 36 6 5%, respectively) compared to an isocaloric diet containing 0.8 g protein/kg per d...

No effect of increasing protein intake during military exercise with severe energy deficit on body composition and performance

“…This lack of an effect may also be related to the study design, as HIGH and LOW were on equally energy‐restricted diets throughout the 10‐day exercise, exposing soldiers in the two groups to similar energy‐dependent catabolic signaling. This perspective is supported by a recent study, wherein an intervention with similar dietary groups (1 g kg −1 d −1 protein vs 2 g kg −1 d −1 protein, isocaloric) and similar levels of energy deficiency (−70%) disclosed no effect of additional protein intake on FFM. The authors thus concluded that increased protein intake during prolonged periods of negative energy balance seems to be used for energy metabolic purposes, which is also supported from findings in another protein supplementation study using isocaloric energy‐restricted diet .…”

“…This perspective is supported by a recent study, wherein an intervention with similar dietary groups (1 g kg −1 d −1 protein vs 2 g kg −1 d −1 protein, isocaloric) and similar levels of energy deficiency (−70%) disclosed no effect of additional protein intake on FFM. The authors thus concluded that increased protein intake during prolonged periods of negative energy balance seems to be used for energy metabolic purposes, which is also supported from findings in another protein supplementation study using isocaloric energy‐restricted diet . Indeed, most studies that reveal beneficial effects of increased protein ingestion on FFM during prolonged periods of energy restriction intake, involve intake of surplus protein as an additive to the regular diet, with a concomitant increase in overall energy intake.…”

“…Surprisingly, FFM remained unchanged from pre‐ to post‐exercise in both groups. This contradicts most previous studies, though it is supported by others, a discrepancy that may be related to considerable variations in study design, including varying degrees of energy deficiency . It is important to note that in the present study, FFM measurements were associated with methodological uncertainty connected to the timing of post‐exercise scanning as discussed in a later paragraph.…”

“…Data from the present study are in the outer‐most part of the specter, despite a relatively low level of physical exhausting activities during the intervention and a relatively short duration compared to other studies . It is thus reasonable to assume that the pronounced impairment in muscular performance was due to the substantial energy deficit, which was estimated to −4320 kcal d −1 (overall energy deficit: −43203 kcal, ~−77%), calculated from changes in fat mass (−4.9 ± 1.4 kg) and FFM (0.5 ± 2.2 kg), resulting in more pronounced loss of fat mass than in many other studies . This is in agreement with a recent meta‐analysis of data from nine military field exercise studies, which observed a decline in lower‐body power and strength as an overall effect of daily energy deficit combined with exercise duration .…”

“…Indeed, overall energy intake and corresponding degrees of energy deficiency may be decisive for whole‐body homeostasis rather than the nature of the energy source ingested (eg, protein vs carbohydrate content) . For example, increased protein intake (1 vs 2 g kg −1 d −1 ) does not seem to hinder loss of muscle mass during 21 days of concomitant severe energy deficit (~−70%) and high altitude exposure in recreationally active men . However, there is evidence to the contrary, as increased protein intake mitigates loss of muscle mass within an isocaloric diet in both resistance‐trained subjects and military personnel undergoing 40% energy deficit, respectively .…”