SCI Rep: Relationship between body mass index variability and diabetes incidence

Background: Type 2 diabetes (T2DM) is an independent risk factor for a range of noncommunicable diseases and a major but preventable cause
of declining quality of life and life expectancy.
According to the Global Burden of Disease (GBD) report, the global prevalence of T2DM increased sharply from about 333 million in 2005 to about 435 million in 2015, and the mortality associated with T2DM increased from 1.
2 million to 1.
5 million per year.

Obesity is strongly associated with prevalent T2DM and T2DM-related mortality and is a major identified but modifiable predictor of T2DM in the general population
.
Weight loss is considered key
to preventing T2DM and its disabling and life-threatening complications.
However, T2DM is not limited to obese individuals, and overweight or normal-weight individuals may also experience the disease, suggesting that T2DM patients include a heterogeneous group
regarding their body mass index (BMI) status in the years prior to diagnosis.

Unlike a single BMI measurement, BMI slope, defined as the overall BMI trend, and BMI variability, defined as intra-individual variability at BMI timeouts, may be able to provide a dynamic longitudinal assessment
of weight trajectories.
Previous epidemiological studies have shown a strong correlation
between increased weight variability and hypertension, cardiovascular disease, and mortality.
However, studies evaluating the association of weight variability with T2DM have been inconsistent
.
In a recent review of 253,766 participants, weight differences increased the risk of T2DM; However, this association did not exist
in males, individuals aged ≤ 60 years, and normal-weight and obese individuals.

Objective: To evaluate the correlation between body mass index variability and slope and the incidence of type 2 diabetes mellitus (T2DM), methods: The study conducted a 15.
8-year sex-stratified follow-up in the population-based
Tehran Lipid and Glucose Study (TLGS).
Of the 10,911 individuals aged 20–60 years, 4981 participants were included and followed for 15.
8 years
.
The slope of body mass index in linear regression models represents the BMI trend
of individuals up to the incidence of diabetes.
The root mean squared error (RMSE) of the linear trend of body mass index was selected to reflect body mass index variability at six
follow-ups.
Cox proportional hazards regression was used to investigate the relationship
between baseline body mass index, body mass index slope, and RMSE with the incidence of T2DM in men and women.

Results: The multivariate-adjusted HR for T2DM per standard deviation increment was 1.
18 (95% CI: 0.
94-1.
48, p = 0.
161) in normal-weight men and 1.
26 (95% CI: 1.
10-1.
44, p = 0.
001)
in overweight and obese men 。 However, in women, for each standard deviation increase in BMI slope, the hazard ratio for normal weight was 1.
19 (95% confidence interval, CI: 1.
01 to 1.
40, p = 0.
039), and the risk ratio for women with a BMI ≥ 25 kg/m2 was 1.
14 (95% confidence interval, CI: 1.
08 to 1.
19, p < 0.
001).

。 In men with a baseline BMI ≥ 25 kg/m2, BMI-RMSE was associated with a reduced risk of T2DM (HR: 0.
71, 95% CI: 0.
53–0.
93, p = 0.
015).

Baseline body mass index for men and women was not associated
with diabetes risk.
The slope of a positive body mass index is associated
with the development of diabetes in both men and women.

Fig.
1 Observed and fitted values
of body mass index changes and residuals of 6 randomly selected male and female participants (left: male, right: female).

Table 1 Baseline characteristics
of the study population.
Categorical variables are expressed
in frequency (percentage).
Continuous variables are expressed as mean ± standard deviation
.
SBP systolic blood pressure, DBP diastolic blood pressure, IGT glucose intolerance, FPG fasting blood glucose, 2-hPG 2-h post-excitation blood glucose, HDL high-density lipoprotein, LDL low-density lipoprotein
.
*Triglyceride levels are reported as median (IQR 25-75).

Table 2 Mean, standard deviation and percentile values
for body mass index variation (RMSE), slope and baseline body mass index.

Table 3 Stratified risk ratio
of sex and body mass index for type 2 diabetes.
Model 1 was adjusted
for age, baseline body mass index, body mass index slope, and body mass index-RMSE.
Model 2 was adjusted
for model 1, as well as family history of diabetes, education, and smoking.
RMSE root mean square error, hazards ratio, confidence interval
.

Conclusion: The association of body mass index variability with T2DM events varied
by sex and baseline body mass index.
Body mass index variation is associated with
a reduced risk of T2DM in overweight and obese men.
Body mass index variation in women and baseline body mass index in men and women were not associated
with T2DM risk.

Mehran L, Mousapour P, Khalili D, et al.
BMI variability and incident diabetes mellitus, Tehran Lipid and Glucose Study (TLGS).
Sci Rep 2022 Nov 01; 12(1)