Early changes in respiratory quotient and resting energy expenditure predict later weight changes in patients treated for poorly controlled type 2 diabetes

Aim: This study looked at whether early changes in resting energy expenditure (REE) and respiratory quotient (RQ) are correlated with later weight changes in patients with type 2 diabetes (T2D) being treated with insulin or GLP-1 analogues, or diet.

Methods: A total of 67 patients (age: 57 ± 9 years; BMI: 33.7 ± 5.0 kg/m(2); HbA1c: 9.9 ± 1.5%) began taking an insulin analogue at bedtime (INS, n=28; initial dose: 0.2 IU/kg) or a GLP-1 analogue (GLP-1, n=23), or only a dietary intervention (diet, n=16; restricted carbohydrates and calories). Their respiratory exchanges were monitored on days 0, 1 and 2 before breakfast.

Results: Two days after starting the bedtime insulin analogue, fasting glycaemia improved (INS: -65 ± 41 mg/dL; GLP-1: -29 ± 48 mg/dL; diet: -31 ± 46 mg/dL; P<0.05), REE decreased (INS: -162 ± 241 kcal/24h; GLP-1: 0 ± 141 kcal/24h; diet: -41 ± 154 kcal/24h; P<0.05) and RQ increased (from 0.76 ± 0.04 to 0.80 ± 0.04; P<0.01), whereas only RQ decreased with diet (from 0.79 ± 0.05 to 0.76 ± 0.04; P<0.05) and remained unchanged with GLP-1 (P<0.005 for ΔRQ across treatments). Only 33 patients attended the scheduled examination three months later. HbA1c improved (INS, n=16: -1.7 ± 1.4%; GLP-1, n=12: -2.1 ± 1.4%; diet, n=5: -1.7 ± 2.8%; NS), while weight changes differed (INS: +1.5 ± 4.3 kg; GLP-1: -2.8 ± 2.8 kg; diet: -2.2 ± 2.7 kg; P<0.005). After three months, weight changes correlated with early changes in REE (r=-0.37, P<0.05) and RQ (r=+0.43, P<0.01), and remained correlated when both changes were included in a multivariate regression analysis (r=0.58, P<0.005).

Conclusion: In poorly controlled patients with T2D and two days after the introduction of a bedtime insulin analogue, REE decreased by -9% while RQ increased by +5%, pointing to a reduction of lipid oxidation. These changes were predictive of later weight gain.