The effects of exercise session timing on weight loss and components of energy balance: midwest exercise trial 2

Abstract

BACKGROUND/OBJECTIVES Circadian physiology has been linked to body weight regulation and obesity. To date, few studies have assessed the association between exercise timing and weight related outcomes. The aim of this secondary analysis was to explore the impact of exercise timing (i.e. 24h clock time of exercise session) on weight loss and components of energy balance. SUBJECTS/METHODS Overweight/obese (BMI 25.0–39.9 kg/m2), physically inactive, young adults (~51% female) completed a 10-month supervised exercise program (400 or 600 kcal/session for 5 days/week) or served as non-exercise controls (CON). Participants were categorized based on the time of day in which they completed exercise sessions (Early-Ex: >50% of sessions completed between 7:00–11:59AM; [n=21], Late-Ex: >50% of sessions completed between 3:00–7:00PM; [n=25], Sporadic-Ex: <50% of sessions completed in any time category; [n=24], and CON; [n=18]). Body weight, energy intake (EI; digital photography), and non-exercise physical activity (NEPA; accelerometer) were assessed at baseline, 3.5, 7 and 10 months. Total daily energy expenditure (TDEE; doubly labeled water), was assessed at baseline and 10 months. RESULTS At month 10, weight loss was significantly greater in both Early-Ex (−7.2±1.2%; p<0.001) and Sporadic-Ex (−5.5±1.2%; p=0.01) vs CON (+0.5±1.0%), and Early-Ex vs Late-Ex (−2.1±1.0%; p<0.001). There were no between group differences for change in TDEE, EI, and non-exercise energy expenditure (P>0.05). A significant group*time interaction (p=0.02) was observed for NEPA (counts/min), however, after adjusting for multiple comparisons, group effects were no longer significant. CONCLUSION Despite minimal differences in components of energy balance, Early-Ex lost significantly more weight compared to Late-Ex. While the mechanisms are unclear, the timing of exercise may be important for body weight regulation.

Later Meal and Sleep Timing Predicts Higher Percent Body Fat

“…Circadian timing of daily behaviors such as energy intake (EI), sleep and physical activity (PA), has emerged as a key factor in the regulation of body weight [ 1 , 2 , 3 ]. The internal circadian timing system in mammals is entrained to a 24-h cycle through light signals reaching a master clock in the hypothalamus [ 4 ] and has evolved to align activities and behaviors (wake, physical activity and eating, versus sleep, inactivity and fasting) with the day/night cycle [ 5 ].…”

Effect of time of day of recreational and household physical activity on prostate and breast cancer risk (MCC‐Spain study)

“…Obesity has been associated with both breast and prostate cancer and may be an additional pathway through which physical activity and timing of physical activity may be associated with lower cancer risk. Higher weight loss 46 and lower total calorie consumption 47 have been observed among persons doing morning exercise compared to exercise in other hours of the day. However, in our analysis, adjusting for BMI and total calorie consumption did not change the cancer risk pattern by timing category.…”

Appetite control and exercise: Does the timing of exercise play a role?

“…between 03:30 pm and 04:30 pm, three times a week [27]. Some authors even observed a 80 to 230 Kcal/day increase in food consumption in response to an afternoon exercise intervention (walking/running on a treadmill), but not when the exercise was set during the morning, in adults with overweight and obesity (noting that these differences did not reach significance) [13]. Such an increase in energy intake after exercise is of main importance to consider since it might decrease the amount of energy expended during the exercise and, in the long term, if the energy expended is overcompensated, this 6 could favor counterproductive results such as weight gain.…”

“…Other studies have questioned the interest of the timing of exercise on sleep [9][10][11], with an evening exercise allowing a better subjective feeling of sleep quality [11] , a decrease in daytime sleepiness [11], a relevant sleep phase progression [9] and a better sympathetic regulation (HR and body temperature) [10]. The exercise-meal timing was also investigated in relation to body composition, with regular pre-meal exercise favoring greater weight loss [12,13], decreased BMI and abdominal circumference [12] and then reducing obesity risks [14].…”