Is obesity related to the lung function of non-asthmatic children?

Table 1 Summary of studies that investigated the impact of overweight/obesity on the plethysmographic indices of lung function

No.	Ref.	No. of children, age range (yr)	Exclusion criteria for the study population	Obesity indices	Plethysmographic variables
1	Li et al[9], 2003	64, 7-18	Children with chronic cardiorespiratory problems	BMI, Trunk Body Fat, and Subtotal Body Fat (total-head). The last 2 indices were calculated as a percentage of body mass	TLC, RV, FRC
2	van de Griendt et al[8], 2012	112, 8.5-18.9	Children diagnosed as asthmatics	BM, WC	TLC, ERV
3	Davidson et al[12], 2014	327, 6-17	Children diagnosed as asthmatics	BMI	TLC, RV, FRC, ERV, VC
4	Rastogi et al[11], 2014	168, 13-18	History of smoking or chronic inflammatory conditions	BMI, WC, Waist-hip ratio	TLC, RV, FRC, RV/TLC, ERV, IC
5	Kongkiattikul et al[10], 2015	45, 8.6-17.3	Children with an underlying pulmonary disease	BMI, WC, WHR Hip circumference Body fat percentage Truncal fat percentage Fat mass index Fat free mass index	TLC, RV, FRC, RV/TLC (only results for FRC were presented)

BMI: Body mass index; TLC: Total lung capacity; RV: Residual volume; FRC: Functional residual capacity; IC: Inspiratory capacity; WC: Waist circumference; WHR: Waist-hip ratio; ERV: Expiratory reserve volume.

Table 2 Summary of studies that investigated the impact of overweight/obesity on spirometric indices of lung function

No.	Ref.	Obesity indices	Study population	Main findings
1	Lazarus et al[34], 1997	Total body fat calculated from equations based on skinfold thickness	Representative sample of 2464 Australian school children aged 9, 12, and 15 yo	Total body fat was inversely associated with FVC and FEV1 after adjusting for height and weight
2	Li et al[9], 2003	Trunk and subtotal (total-head) body fat mass	Sixty-four obese children, 7-18 yo without cardiorespiratory problems.	No significant associations between the obesity and the spirometric indices
3	Perez-Padilla et al[35], 2006	Trunk body fat	A cross-sectional study of 6784 students 6-20 yo	In children < 11 yr FEV1 and FVC increased with BMI. In subjects > 12 yr lung function increased with BMI, reached a plateau (at a BMI Z score of 1SD) and then decreased among those with highest BMI
4	Nageswari et al[36], 2007	% body mass	Twenty obese/overweight children and 20 normal-weight (controls), 12-16 yo	FEV1, FVC, FEF25%-75% were significantly lower in the obese group compared to the controls
5	Chen et al[18], 2009	Subtotal body fat (total-head)	A cross-sectional study of 718 children 6-17 yo	WC, but not BMI, was positively associated with FEV1 and FVC, and negatively associated with FEV1/FVC
6	Spathopoulos et al[37], 2009	% body mass	Three hundred fifty-seven overweight, 300 obese, and 196 normal-weight children. Not well-controlled asthma cases were excluded	All spirometric parameters were significantly different across the three groups. BMI > 85th centile was a significant independent predictor of reduced spirometric parameters after controlling for confounders
7	Cibella et al[16], 2011	BMI	Cross-sectional study carried out in a sample of 708 children 10-16 yo	FEV1 and FVC were lower in children with BMI > 85th centile compared to those with normal BMI. No difference was found for FEF25%-75%, FEV1/FVC
8	Feng et al[19], 2012	BMI	A cross-sectional performed on 1572 healthy children 9-18 yo. Children with asthma were excluded	WC was inversely associated with FEV1, FVC and FEV1/FVC. BMI was positively related with FEV1 and FVC and negatively associated with FEV1/FVC
9	van de Griendt et al[8], 2012	BMI	One hundred twelve obese children 8.5-18.9 yo, taking part in a multidisciplinary treatment programme.	FEV1 and FVC increased by 2.91% and 3.08% after weight reduction following a 6 mo intervention program and this increase was significant. No significant change was observed in MEF50
10	Paralikar et al[38], 2012	WC	Thirty obese boys 12-17 yo and 30 age-matched normal-weight boys	FEV1, FEV1/FVC and MVV were significantly decreased in the obese group
11	Bekkers et al[20], 2013	BMI, WC	Children from a birth cohort (n = 1058) examined at the age of 8 yo	Large WC in girls was associated with lower FEV1 /FVC ratio
12	Davidson et al[12], 2013	BMI	Three hundred twenty-seven children 6-17 yo referred for lung testing due to various respiratory problems. Individuals with cardiopulmonary, chest wall disease, or asthma, were excluded	Positive relationship between BMI z-score and percent predicted FVC, and VC. Negative relationship between BMI z-score and FRC, ERV, RV, and FEV1/FVC
13	Han et al[17], 2014	BMI, PBF, WC	Cross-sectional study in 2681 children 6-17 yo	Among children without asthma, BMI, PBF, and WC were associated with higher FEV1 and FVC, and lower FEV1/FVC
14	Khan et al[39], 2014	BMI, WC, WHR, skinfold measurements	A sample of 1583 children, < 18 yo. No data on asthma diagnosis was provided	Overweight/obese boys, had WC and WHR inversely associated with residual FVC, FEV0.75, and FEV1
15	Rastogi et al[11], 2014	BMI	A sample of 168 adolescents, 13-18 yo, irrespective of asthma status	Obese adolescents had lower RV, RV/TLC ratio, ERV, and FRC, and higher IC adolescents; the 2 groups did not differ in measures of lower airway obstruction, namely FEV1/FVC, and MEF
16	Torun et al[40], 2014	BMI	A cross-sectional study of 30 overweight, 34 obese and 64 morbidly obese children, 9-17 yo, referred to a paediatric endocrinology dept. Asthmatic patients were excluded from the study	PEF and FEV25–75 were significantly reduced in in the overweight, obese and morbidly obese children
17	Bekkers et al[41], 2015	BMI, WC	Children from a birth cohort examined at the ages of 8 yo (n = 1090) and 12 yo (n = 1288)	At 8 yo, large WC was associated with lower FEV1/FVC after adjusting for BMI (only in girls)
18	Kongkiattikul et al[10], 2015	BMI, FMI, body fat percentage, truncal fat percentage, mean fat free mass index	Forty-five obese children, 8-18 yo	Negative correlation between FRC and almost all obesity indices
19	Cibella et al[14], 2015	BMI	A cross-sectional study of 2393 healthy children 10-17 yo. Children with asthma were excluded	FVC and FEV1 were positively but disproportionately correlated to weight. FEV1/FVC and FEF25-75%/FVC ratios were negatively correlated to weight
20	Costa Junior et al[42], 2016	BMI, WC, body composition (tetrapolar bioimpedance)	A cross-sectional study of 40 obese and 35 normal-weight children, 6-10 yo. Children with respiratory problems were excluded	Obese children had lower FEV1 and FEV1/FVC
21	Liyanage et al[13], 2016	BMI	A cross-sectional study of 55 obese and 220 normal-weight children, 9-15 yo. Children with asthma were excluded	No significant difference in spirometric values
22	Akin et al[43], 2017	BMI, WC, neck circumference	A cross-sectional study of 178 children, 5 to 15 yo. Children with asthma were excluded	Negative correlation between FEV1, FEV1/FVC, and obesity indices
23	Yao et al[15], 2017	BMI	1717 children, 5 to 18 yo, irrespective of asthma status	BMI is associated positively with FVC, FEV1, and PEF, and FEF25-75, but negatively with FEV1/FVC

yo: Years old; PBF: Percent body fat; WHR: Waist-to-hip ratio; MVV: Maximum voluntary ventilation; BMI: Body mass index; WC: Waist circumference; WHR: Waist-hip ratio; FEV1: Forced expiratory volume in 1 s; FVC: Forced vital capacity.