Response to Letter to the Editor: “Twice as High Diet-Induced Thermogenesis After Breakfast vs Dinner on High-Calorie as well as Low-Calorie Meals”

Influence of Fasting until Noon (Extended Postabsorptive State) on Clock Gene mRNA Expression and Regulation of Body Weight and Glucose Metabolism

“…The clock gene regulation also enhances insulin sensitivity, β-cell responsiveness, GLUT-4 activity, muscle glucose uptake, post-meal incretin (i.e., GLP-1, GLP-2, and GIP) secretion, and incretin-mediated insulinotropic effect in the early hours of the active phase [ 58 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 68 ]. As a result, the glycemic response is significantly higher after identical meals consumed in the evening compared to the morning [ 18 , 36 , 58 , 78 , 79 , 80 ].…”

“…The resting energy expenditure (REE) also displays circadian oscillation showing its lowest levels during the resting phase, while the respiratory quotient (RQ), reflecting macronutrient utilization, is at its highest score in the early hours of the active phase [ 81 ]. Moreover, the circadian clock enhances diet-induced thermogenesis (DIT) or energy expenditure after meals consumed in the early active phase compared to the evening [ 34 , 35 , 36 , 37 ]. Therefore, the early hours of the active phase (i.e., breakfast) are optimal for food intake and especially for CH consumption, while in the evening and nighttime, it is likely more convenient to reduce the energy and CH intake [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 69 , 70 , 77 , 78 , 79 , 80 , 81 ].…”

“…It enhances enzymes and hormones involved in the regulation of body weight [ 19 , 23 , 24 , 25 ], overall glycemia [ 18 , 26 , 27 , 28 , 29 ], muscle synthesis [ 30 , 31 , 32 ], and appetite [ 12 , 25 , 33 ]. Further, the diet-induced thermogenesis is significantly higher after a high-energy breakfast vs. an isocaloric dinner, highlighting the importance of the first meal of the day in achieving metabolic homeostasis [ 25 , 34 , 35 , 36 , 37 ].…”

“…The omission of breakfast has been associated with higher body mass indices, insulin resistance, hyperglycemia, and the risk for developing T2D [ 19 , 23 , 28 , 39 , 40 , 41 , 42 , 43 ]. The circadian misalignment and disrupted clock gene expression arising from fasting until noon leads to increased glycemia and appetite scores, deficient insulin and incretin responses after subsequent meals [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 27 , 38 , 44 , 45 , 46 ], and diminished energy expenditure [ 25 , 34 , 35 , 36 , 37 ]. Further, the lack of breakfast activates muscle protein breakdown to provide the liver with glucogenic amino acids for neoglucogenesis, which may result in a loss of skeletal muscle mass [ 30 , 31 , 32 , 41 , 45 , 46 , 47 ].…”

Reciprocal Interactions between Circadian Clocks, Food Intake, and Energy Metabolism

“…Furthermore, other hormones that can impact the optional DIT, such as adrenaline or noradrenaline, have higher levels at the beginning of the active phase. As schematized in Figure 2 , DIT in humans is considered higher in the morning compared to the evening [ 14 , 15 , 16 ]. These daily variations in DIT, however, have been recently challenged because they can be explained by circadian changes in the resting metabolic rate [ 17 ].…”