Effect of ambient temperature on overweight: direct and indirect pathways in a multiple mediation model

Baker, Julia Mariel Wirtz; Aballay, Laura Rosana; Osella, Alberto Rubén; Lambert, Victoria; Pou, Sonia Alejandra

doi:10.1590/0102-311XEN090225

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ARTICLE • Cad. Saúde Pública 41 (11) • 2025 • https://doi.org/10.1590/0102-311XEN090225 linkcopy

Effect of ambient temperature on overweight: direct and indirect pathways in a multiple mediation model

Efecto de la temperatura ambiente sobre el sobrepeso: vías directas e indirectas en un modelo de mediación múltiple

Efeito da temperatura ambiente no sobrepeso: vias diretas e indiretas em um modelo de mediação múltipla

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstracts

Global warming and obesity are two major global challenges. The intricate relationships between climate, lifestyle factors, and their combined impact on overweight remain to be fully elucidated. We aim to estimate the effect of ambient temperature on overweight and examine the role of physical activity and fruit/vegetable consumption as indirect mediating pathways in Argentina. This cross-sectional study was conducted using data from the 2018 National Risk Factors Survey. Average air-temperature at 2m height (from ERA5 reanalysis data) was linked with individual-level data. A multilevel logistic generalized structural equation model was applied to examine the mediating effects of physical activity level and fruit/vegetable consumption on the association between ambient temperature and overweight, adjusted for sex, age, and educational level. The raw difference (95%CI) between the indirect effects was estimated using bootstrapping techniques (sample = 10,000, replicates = 5,000). An inverse association (direct effect) was observed between ambient temperature and overweight (c = -0.019, 95%CI: -0.034; -0.004). A one-unit increase in temperature was associated with higher log odds of fruit/vegetable consumption (a₁ = 0.020, 95%CI: 0.005; 0.035) and lower log odds of having moderate (a₂₁ = -0.015, 95%CI: -0.023; -0.007) and high (a₂₂ = -0.059, 95%CI: -0.068; -0.049) physical activity levels, compared to low fruit/vegetable consumption and low physical activity level, respectively. However, the mediating effect of high physical activity level on the temperature-overweight relationship was of greater magnitude. In conclusion, ambient temperature influences fruit/vegetable consumption and physical activity, indirectly affecting nutritional status, with physical activity acting as the key mediator. This underscores the need to prioritize climate change adaptation strategies that promote physical activity.

Keywords:
Climate; Overweight; Mediation Analysis; Physical Activities

Characteristics	Overweight				Total (n = 16,410)		p-value
	No (n = 5,268)		Yes (n = 11,142)
	Mean	SD	Mean	SD	Mean	SD
Age (years)	40.1	18.2	49.0	17.1	46.1	17.9	< 0.001
Variables	Count	%	Count	%	Count	%
Sex
Male	1,988	38	4,972	45	6,960	42	< 0.001
Female	3,280	62	6,170	55	9,450	58
Education
Incomplete primary school	365	7	1,282	12	1,647	10	< 0.001
Incomplete secondary school	1,656	31	4,250	38	5,906	36
Complete secondary school	2,165	41	3,847	35	6,012	37
Tertiary or university	1,082	21	1,763	16	2,845	17
Physical activity
Low	2,125	40	5,549	50	7,674	47	< 0.001
Moderate	1,985	38	3,855	35	5,840	36
High	1,158	22	1,738	16	2,896	18
Fruit/Vegetable consumption (≥ 5 servings/day)
No	4,812	94	10,168	94	14,980	94	0.345
Yes	299	6	676	6	975	6

Overweight (outcome)	Crude model		Model 1		Model 2		Model 3		Model 4
Overweight (outcome)	Coefficient	95%CI	Coefficient	95%CI	Coefficient	95%CI	Coefficient	95%CI	Coefficient	95%CI
Mean 2m-air temperature (continuous)	-0.013	-0.027; 0.001	-0.013	-0.027; 0.001	-0.016	-0.032; -0.0003	-0.019	-0.034; -0.004	-0.019	-0.034; -0.004
Age (continuous)	0.030	0.028; 0.032			0.031	0.028; 0.032	0.029	0.027; 0.031	0.029	0.027; 0.031
Sex (male as reference)
Female	-0.290	-0.358; -0.223			-0.330	-0.399; -0.260	-0.365	-0.437; -0.293	-0.365	-0.437; -0.293
Education (university as reference)
Incomplete primary school	0.743	0.602; 0.883			0.299	0.152; 0.446	0.269	0.119; 0.420	0.269	0.119; 0.420
Incomplete secondary school	0.423	0.327; 0.519			0.338	0.239; 0.438	0.317	0.216; 0.418	0.317	0.216; 0.418
Complete secondary school	0.059	-0.033; 0.152			0.222	0.126; 0.319	0.208	0.110; 0.306	0.208	0.110; 0.306
Physical activity (low level as reference)
Moderate	-0.290	-0.365; -0.152					-0.168	-0.247; -0.090	-0.168	-0.247; -0.090
High	-0.567	-0.658; -0.476					-0.362	-0.460; -0.264	-0.362	-0.460; -0.264
Fruit and vegetable consumption (< 5 servings/day as reference)
≥ 5 servings/day	0.049	-0.092; 0.191					0.025	-0.123; 0.173	0.025	-0.123; 0.173
Moderate physical activity (outcome)
Mean 2m-air temperature (continuous)									-0.015	-0.023; -0.007
High physical activity (outcome)
Mean 2m-air temperature (continuous)									-0.059	-0.068; -0.049
Fruits and vegetables consumption (outcome)
Mean 2m-air temperature (continuous)									0.020	0.005; 0.035
Area-level clustering			Variance	SE	Variance	SE	Variance	SE	Variance	SE
Province			0.023	0.008	0.030	0.011	0.026	0.010	0.026	0.010

Mediation paths	Coefficients	Value	SE	95%CI
X → M₁	a₁	0.020	0.007	0.005; 0.035
M1 → Y	b₁	0.018	0.072	-0.123; 0.160
X → M₂₁	a₂₁	-0.015	0.003	-0.023; -0.007
M₂₁ → Y	b₂₁	-0.234	0.038	-0.310; -0.159
X → M₂₂	a₂₂	-0.059	0.004	-0.068; -0.049
M₂₂ → Y	b₂₂	-0.413	0.051	-0.514; -0.311
Direct effects
X → Y	c	-0.021	0.005	-0.032; -0.009
Indirect effects
X → M₁ → Y	a₁ b₁	0.0003	0.002	-0.003; 0.004
X → M₂₁ → Y	a₂₁ b₂₁	0.003	0.001	0.0007; 0.006
X → M₂₂ → Y	a₂₂ b₂₂	0.024	0.004	0.015; 0.033
	Estimators	Value	Boot SE	95% Boot CI
Total effects
Direct plus Path ₁	c + a₁ b₁	-0.020	0.005	-0.031; -0.009
Direct plus Path ₂₁	c + a₂₁ b₂₁	-0.017	0.005	-0.028; -0.006
Direct plus Path ₂₂	c + a₂₂ b₂₂	0.003	0.006	-0.009; 0.016
Metrics of difference
Raw difference M₁ vs. M₂₁	a₁b₁ − a₂₁b₂₁	-0.030	0.002	-0.001; 0.008
Raw difference M₁ vs. M₂₂	a₁b₁ − a₂₂b₂₂	0.024	0.005	0.014; 0.034

Mediation paths	Coefficients	Value	SE	95%CI
X → M₁	a₁	0.020	0.007	0.005; 0.035
M₁ → Y	b₁	0.025	0.075	-0.123; 0.173
X → M₂₁	a₂₁	-0.015	0.003	-0.023; -0.007
M₂₁ → Y	b₂₁	-0.168	0.040	-0.247; -0.090
X → M₂₂	a₂₂	-0.059	0.004	-0.068; -0.049
M₂₂ → Y	b₂₂	-0.362	0.049	-0.460; -0.264
Direct effects
X → Y	c	-0.019	0.007	-0.034;-0.004
		Value	Boot SE	95% Boot CI
Indirect effects
X → M₁ → Y	a₁ b₁	0.0005	0.002	-0.003; 0.004
X → M₂₁ → Y	a₂₁ b₂₁	0.002	0.001	0.0002; 0.0004
X → M₂₂ → Y	a₂₂ b₂₂	0.021	0.004	0.012; 0.030
	Estimators	Value	Boot SE	95% Boot CI
Total effects
Direct plus Path ₁	c + a₁ b₁	-0.019	0.005	-0.030; -0.007
Direct plus Path ₂₁	c + a₂₁ b₂₁	-0.016	0.005	-0.027; -0.005
Direct plus Path ₂₂	c + a₂₂ b₂₂	0.002	0.006	-0.010; 0.015
Metrics of difference
Raw difference M₁ vs. M₂₁	a₁b₁ − a₂₁b₂₁	0.002	0.002	-0.002; 0.006
Raw difference M₁ vs. M₂₂	a₁b₁ − a₂₂b₂₂	0.020	0.004	0.001; 0.030

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[TFN1] SD: standard deviation.