Background This systematic review aims to identify the effects of exercise interventions in patients with breast cancer (BCP) and survivors (BCS) on selected variables of physical fitness. Methods A comprehensive literature search was conducted using Medline and Scopus. Randomized controlled trials with isolated exercise interventions in BCP and BCS women (< 5 years from therapy completion) were included. The risk of bias (RoB) assessment was conducted using the Cochrane RoB-2-tool. Variables regarding cardiorespiratory fitness (CRF), strength (ST), fatigue (F) and health-related quality of life (HRQoL) were discussed. Results Of the 336 studies initially identified, 22 met all the inclusion criteria and were deemed eligible. RoB assessment indicated that the studies had predominantly “some concerns” or had “low RoB”, with only 3 studies presenting a “high RoB”. The mean duration and frequency of exercise interventions were 19 weeks and 3 sessions/week, performed at moderate intensity (65% VO2max and 66% 1RM, for aerobic and resistance-training interventions, respectively). Conclusions Exercise interventions seem to be a valuable strategy in BCP to avoid the decline of CRF, ST, F and HRQoL. Conversely, improved physical function among BCS is observed for the same variables. Resistance training and combined interventions seem to provide the most encouraging variations of the selected outcomes. PROSPERO registration ID CRD42021237917.

Objective To characterize the contributions of the loss of energy-expending tissues and metabolic adaptations to the reduction in resting metabolic rate (RMR) following weight loss. Methods A secondary analysis was conducted on data from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy study. Changes in RMR, body composition, and metabolic hormones were examined over 12 months of calorie restriction in 109 individuals. The contribution of tissue losses to the decline in RMR was determined by weighing changes in the size of energy-expending tissues and organs (skeletal muscle, adipose tissue, bone, brain, inner organs, residual mass) assessed by dual-energy X-ray absorptiometry with their tissue-specific metabolic rates. Metabolic adaptations were quantified as the remaining reduction in RMR. Results RMR was reduced by 101 ± 12 kcal/d as participants lost 7.3 ± 0.2 kg (both p < 0.001). On average, 60% of the total reduction in RMR were explained by energy-expending tissues losses, while 40% were attributed to metabolic adaptations. The loss of skeletal muscle mass (1.0 ± 0.7 kg) was not significantly related to RMR changes (r = 0.14, p = 0.16), whereas adipose tissue losses (7.2 ± 3.0 kg) were positively associated with the reduction in RMR (r = 0.42, p < 0.001) and metabolic adaptations (r = 0.31, p < 0.001). Metabolic adaptations were correlated with declines in leptin (r = 0.27, p < 0.01), triiodothyronine (r = 0.19, p < 0.05), and insulin (r = 0.25, p < 0.05). Conclusions During weight loss, tissue loss and metabolic adaptations both contribute to the reduction in RMR, albeit variably. Contrary to popularly belief, it is not skeletal muscle, but rather adipose tissue losses that seem to drive RMR reductions following weight loss. Future research should target personalized strategies addressing the predominant cause of RMR reduction for weight maintenance.

Exercise is commonly utilized for weight loss, yet research has focused less on specific modifications to adipose tissue metabolism. White adipose tissue (WAT) is the storage form of fat, whereas brown adipose tissue (BAT) is a thermogenic tissue whose uncoupling increases energy expenditure. The most established BAT activator is cold exposure, which also transforms WAT into “beige cells” that express uncoupling protein 1 (UCP1). Preliminary evidence in rodents suggests exercise elicits similar effects. The purpose of this review is to parallel and examine differences between exercise and cold exposure on BAT activation and beige induction. Like cold exposure, exercise stimulates the sympathetic nervous system and activates molecular pathways responsible for BAT/beige activation, including upregulation of BAT activation markers (UCP1, proliferator-activated receptor-gamma coactivator-1α) and stimulation of endocrine activators (fibroblast growth factor-21, irisin, and natriuretic peptides). Further, certain BAT activators are altered exclusively by exercise (interleukin-6, lactate). Markers of BAT activation increase from both cold exposure and exercise, whereas effects in WAT are compartment-specific. Stimulation of endocrine activators depends on numerous factors, including stimulus intensity and duration. Evidence of these analogous, albeit not mirrored, mechanisms is demonstrated by increases in adipose activity in rodents, while effects remain challenging to quantify in humans.

Although exercise modulates appetite regulation and food intake, it remains poorly understood how exercise impacts decision-making about food. The purpose of the present study was to assess the impact of an acute exercise bout on hypothetical choices related to the amount and timing of food intake. Forty-one healthy participants (22.0 ± 2.6 years; 23.7 ± 2.5 kg/m2, 56% female) completed 45 min of aerobic exercise and a resting control condition in randomized order. Food amount preferences and intertemporal food preferences (preference for immediate vs. delayed consumption) were assessed using electronic questionnaires with visual food cues. Compared to rest, exercise resulted in a greater increase in the food amount selected, both immediately post-exercise (+25.8 ± 11.0 vs. +7.8 ± 11.0 kcal/item, p = 0.02) and 30 min post-exercise (+47.3 ± 12.4 vs. +21.3 ± 12.4 kcal/item, p = 0.005). Exercise further resulted in a greater increase in the preference for immediate consumption immediately post-exercise (+0.23 ± 0.10 vs. +0.06 ± 0.10; p = 0.03) and 30 min post-exercise (+0.30 ± 0.12 vs. +0.08 ± 0.12; p = 0.01). Our findings demonstrate that a single bout of aerobic exercise shifts hypothetical food choices toward greater amounts and more immediate consumption, highlighting the importance of the timing of food choices made in the exercise context.

Energy availability describes the amount of dietary energy remaining for physiological functionality after the energy cost of exercise is deducted. The physiological and hormonal consequences of low energy availability (LEA) are well established, but the impact of LEA on physical activity behavior outside of exercise and, specifically, nonexercise activity thermogenesis (NEAT) has not been systematically examined. The authors conducted a secondary analysis of a repeated-measures crossover study in which recreationally trained young men (n = 6, 25 ± 1.0 years) underwent two 4-day conditions of LEA (15 kcal·kg fat-free mass−1 ·day−1) with and without endurance exercise (LEA + EX and LEA EX) and two energy-balanced control conditions (CON + EX and CON EX). The duration and intensity of physical activity outside of prescribed exercise were assessed using the SenseWear Pro3 armband. LEA did not alter NEAT (p = .41), nor time spent in moderate to vigorous (p = .20) and low-intensity physical activity (p = .17). However, time spent in low-intensity physical activity was lower in LEA + EX than LEA − EX (13.7 ± 0.3 vs. 15.2 ± 0.3 hr/day; p = .002). Short-term LEA does not seem to impact NEAT per se, but the way it is attained may impact physical activity behavior outside of exercise. As the participants expended similar amounts of energy during NEAT (900–1,300 kcal/day = 12.5–18.0 kcal·kg fat-free mass−1·day−1) and prescribed exercise bouts (15.0 kcal·kg fat-free mass−1·day−1), excluding it as a component of energy expenditure may skew the true energy available for physiological functionality in active populations.

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Objectives Weight loss, especially when achieved by caloric restriction (CR), reduces total daily energy expenditure (EE), which can attenuate further weight loss. Although exercise is a common countermeasure to the decline in EE, it is unknown whether prescribed exercise leads to compensatory changes in moderate-to-vigorous physical activities (MVPA) during non-exercise periods in the context of CR. The present study sought to quantify changes in MVPA in response to an energetically-matched energy deficit induced by CR alone or combined with exercise. We hypothesized that MVPA outside of prescribed exercise would be greater during non-exercise conditions, regardless of energy balance. Methods In a repeated-measures crossover design, active men (n = 6, 25 ± 1.0 y) underwent four 4-day conditions: CR with exercise (CR + X), CR without exercise (CR–X), energy-balanced control (CON) with exercise (CON + X) and without exercise (CON–X). Dietary intake was manipulated such that energy availability (EA) was 15 kcal·kg FFM−1·day−1 (CR) or 40 kcal·kg FFM−1·day−1 (CON). Prescribed exercise EE was 15 kcal·kg FFM−1·day−1. Physical activity was assessed using the SenseWear Pro3 armband (Bodymedia, Pittsburgh, USA) to quantify time spent in MVPA and light activities (sleep, lying down without sleep, and non-lying light activities) as % of total wear time. Results EA did not differ between CR (P = 0.87) nor CON (P = 0.42). As expected, weight loss was significant (P < 0.001) in CR + EX (–1.8 ± 0.4 kg) and CR-EX (–2.4 ± 0.3 kg). After deducting prescribed exercise, there was a significant effect of exercise on time spent in MVPA (P = 0.02), in that MVPA was lower during CON-EX vs. CON + EX (11.4 ± 2.0% vs. 17.9 ± 2.1%, P = 0.03) and trended lower during CR-EX vs. CR + EX (13.6 ± 1.5% vs. 15.5 ± 1.6%, P = 0.08). In exercise conditions, MVPA was lower during CR + EX when compared to CON + EX (P = 0.03). Conclusions Independent of energy balance, engaging in short-term exercise led to more, not less, time spent in non-exercise MVPA. These findings indicate the prevention of reductions in non-exercise activity as an additional benefit of incorporating exercise into weight loss interventions. Funding Sources The study was supported in part by the USDA National Institute of Food and Agriculture and institutional funding from the University of Nebraska-Lincoln.

Objectives Laboratory experiments suggest that exercise can modulate appetite regulation and ad libitum food intake, but the impact of exercise on decision making about food remains poorly understood. As such, this study sought to assess the impact of an acute exercise bout on food choices, in particular, the amount and taste preference for immediate and delayed consumption. Methods 18 male and 23 female participants (age: 22.0 ± 2.6 years; BMI: 23.7 ± 2.5 kg/m2; VO2peak: 37.3 ± 6.2 mL/kg/min) completed two experimental conditions, a 45-min exercise bout at 60% of VO2peak (EX) and a 45-min resting period (R), in a randomized, cross-over design. Electronic questionnaires to assess prospective food consumption, temporal preference (now vs. delayed consumption), and ratings of appetite and hunger were employed immediately before, immediately after, and 30 min after completion of the EX/R task. Questionnaires provided visual cues of hypothetical food items to assess preferences for different portion sizes as well as binary choices between food items with varying fat content and sweetness. Results There were main condition effects for exercise both immediately (P = 0.02) and 30 min after the task (P = 0.004), demonstrating that EX resulted in increased prospective food consumption for immediate consumption (after task: 41.2 ± 90.7 kcal (EX) vs. 16.0 ± 74.2 kcal (R); 30 min after task: 78.7 ± 107.6 kcal (EX) vs. 46.6 ± 85.2 kcal (R)) and delayed consumption (after task: 10.5 ± 85. 9 kcal (EX) vs. −0.5 ± 73.6 kcal (R); 30 min after task (16.0 ± 88.2 kcal (EX) vs. −4.1 ± 95.2 kcal (R)). Fat content and sweetness did not impact prospective consumption immediately (both P > 0.32) or 30 min after the task (both P > 0.11). Exercise further resulted in an increased preference for immediate vs. delayed consumption both immediately (P = 0.02) and 30 min after the task (P = 0.02). Conclusions Our findings indicate that exercise acutely shifts food choices towards greater amounts and a preference for more immediate food consumption, highlighting the importance of the timing of food choices in the context of exercise. Funding Sources This work was funded by a Food for Health Collaboration Initiative grant by the University of Nebraska.