Maternal Prepregnancy Body Mass Index and Gestational Weight Gain on Pregnancy Outcomes

Objective

The aim of the present study was to evaluate the single and joint associations of maternal prepregnancy body mass index (BMI) and gestational weight gain (GWG) with pregnancy outcomes in Tianjin, China.

Methods

Between June 2009 and May 2011, health care records of 33,973 pregnant women were collected and their children were measured for birth weight and birth length. The independent and joint associations of prepregnancy BMI and GWG based on the Institute of Medicine (IOM) guidelines with the risks of pregnancy and neonatal outcomes were examined by using Logistic Regression.

Results

After adjustment for all confounding factors, maternal prepregnancy BMI was positively associated with risks of gestational diabetes mellitus (GDM), pregnancy-induced hypertension, caesarean delivery, preterm delivery, large-for-gestational age infant (LGA), and macrosomia, and inversely associated with risks of small-for-gestational age infant (SGA) and low birth weight. Maternal excessive GWG was associated with increased risks of pregnancy-induced hypertension, caesarean delivery, LGA, and macrosomia, and decreased risks of preterm delivery, SGA, and low birth weight. Maternal inadequate GWG was associated with increased risks of preterm delivery and SGA, and decreased risks of LGA and macrosomia, compared with maternal adequate GWG. Women with both prepregnancy obesity and excessive GWG had 2.2–5.9 folds higher risks of GDM, pregnancy-induced hypertension, caesarean delivery, LGA, and macrosomia compared with women with normal prepregnancy BMI and adequate GWG.

Conclusions

Maternal prepregnancy obesity and excessive GWG were associated with greater risks of pregnancy-induced hypertension, caesarean delivery, and greater infant size at birth. Health care providers should inform women to start the pregnancy with a BMI in the normal weight category and limit their GWG to the range specified for their prepregnancy BMI.     

Maternal Prepregnancy Body Mass Index and Gestational Weight Gain on Offspring Overweight in Early Infancy

Objective

The aim of the present study was to evaluate the association of maternal prepregnancy body mass index (BMI) and gestational weight gain (GWG) with anthropometry in the offspring from birth to 12 months old in Tianjin, China.

Methods

Between 2009 and 2011, health care records of 38,539 pregnant women had been collected, and their children had been measured body weight and length at birth, 3, 6, 9 and 12 months of age. The independent and joint associations of pre-pregnancy BMI and GWG based on the Institute of Medicine (IOM) guidelines with anthropometry in the offspring were examined using General Linear Model and Logistic Regression.

Results

Prepregnancy BMI and maternal GWG were positively associated with Z-scores for birth weight-for-gestational age, birth length-for-gestational age, and birth weight-for-length. Infants born to mothers with excessive GWG had the greatest changes in Z-scores for weight-for-age from birth to Month 3, and from Month 6 to Month 12, and the greatest changes in Z-scores for length-for-age from birth to months 3 and 12 compared with infants born to mothers with adequate GWG. Excessive GWG was associated with an increased risk of offspring overweight or obesity at 12 months old in all BMI categories except underweight.

Conclusions

Maternal prepregnancy overweight/obesity and excessive GWG were associated with greater weight gain and length gain of offspring in early infancy. Excessive GWG was associated with increased infancy overweight and obesity risk.     

Pre-Pregnancy Body Mass Index,Gestational Weight Gain,and Birth Weight: A Cohort Study in China

Objective

To assess whether pre-pregnancy body mass index (BMI) modify the relationship between gestational weight gain (GWG) and child birth weight (specifically, presence or absence of low birth weight (LBW) or presence of absence of macrosomia), and estimates of the relative risk of macrosomia and LBW based on pre-pregnancy BMI were controlled in Wuhan, China.

Methods

From June 30, 2011 to June 30, 2013. All data was collected and available from the perinatal health care system. Logistic regression models were used to estimate the independent association among pregnancy weight gain, LBW, normal birth weight, and macrosomia within different pre-pregnancy BMI groups. We built different logistic models for the 2009 Institute of Medicine (IOM) Guidelines and Chinese-recommended GWG which was made from this sample. The Chinese-recommended GWG was derived from the quartile values (25th-75th percentiles) of weight gain at the time of delivery in the subjects which comprised our sample.

Results

For LBW children, using the recommended weight gain of the IOM and Chinese women as a reference, the OR for a pregnancy weight gain below recommendations resulted in a positive relationship for lean and normal weight women, but not for overweight and obese women. For macrosomia, considering the IOM’s recommended weight gain as a reference, the OR magnitude for pregnancy weight gain above recommendations resulted in a positive correlation for all women. The OR for a pregnancy weight gain below recommendations resulted in a negative relationship for normal BMI and lean women, but not for overweight and obese women based on the IOM recommendations, significant based on the recommended pregnancy weight gain for Chinese women. Of normal weight children, 56.6% were above the GWG based on IOM recommendations, but 26.97% of normal weight children were above the GWG based on Chinese recommendations.

Conclusions

A GWG above IOM recommendations might not be helpful for Chinese women. We need unified criteria to classify adult BMI and to expand the sample size to improve representation and to elucidate the relationship between GWG and related outcomes for developing a Chinese GWG recommendation.     

Joint and Independent Associations of Gestational Weight Gain and Pre-Pregnancy Body Mass Index with Outcomes of Pregnancy in Chinese Women: A Retrospective Cohort Study

Objective

To explore the joint and independent effects of gestational weight gain (GWG) and pre-pregnancy body mass index (BMI) on pregnancy outcomes in a population of Chinese Han women and to evaluate pregnant women’s adherence to the 2009 Institute of Medicine (IOM) gestational weight gain guidelines.

Methods

This was a multicenter, retrospective cohort study of 48,867 primiparous women from mainland China who had a full-term singleton birth between January 1, 2011 and December 30, 2011. The independent associations of pre-pregnancy BMI, GWG and categories of combined pre-pregnancy BMI and GWG with outcomes of interest were examined using an adjusted multivariate regression model. In addition, women with pre-pregnancy hypertension were excluded from the analysis of the relationship between GWG and delivery of small-for-gestational-age (SGA) infants, and women with gestational diabetes (GDM) were excluded from the analysis of the relationship between GWG and delivery of large-for-gestational-age (LGA) infants.

Results

Only 36.8% of the women had a weight gain that was within the recommended range; 25% and 38.2% had weight gains that were below and above the recommended range, respectively. The contribution of GWG to the risk of adverse maternal and fetal outcomes was modest. Women with excessive GWG had an increased likelihood of gestational hypertension (adjusted OR 2.55; 95% CI = 1.92–2.80), postpartum hemorrhage (adjusted OR 1.30; 95% CI = 1.17–1.45), cesarean section (adjusted OR 1.31; 95% CI = 1.18–1.36) and delivery of an LGA infant (adjusted OR 2.1; 95% CI = 1.76–2.26) compared with women with normal weight gain. Conversely, the incidence of GDM (adjusted OR 1.64; 95% CI = 1.20–1.85) and SGA infants (adjusted OR 1.51; 95% CI = 1.32–1.72) was increased in the group of women with inadequate GWG. Moreover, in the obese women, excessive GWG was associated with an apparent increased risk of delivering an LGA infant. In the women who were underweight, poor weight gain was associated with an increased likelihood of delivering an SGA infant. After excluding the mothers with GDM or gestational hypertension, the ORs for delivery of LGA and SGA infants decreased for women with high GWG and increased for women with low GWG.

Conclusions

GWG above the recommended range is common in this population and is associated with multiple unfavorable outcomes independent of pre-pregnancy BMI. Obese women may benefit from avoiding weight gain above the range recommended by the 2009 IOM. Underweight women should avoid low GWG to prevent delivering an SGA infant. Pregnant women should therefore be monitored to comply with the IOM recommendations and should have a balanced weight gain that is within a range based on their pre-pregnancy BMI.     

Free-Triiodothyronine to Free-Thyroxine Ratio Mediated the Effect of Prepregnancy Body Mass Index or Maternal Weight Gain During Early Pregnancy on Gestational Diabetes Mellitus

ObjectiveMaternal overweight or obesity during early pregnancy can increase the subsequent risk of gestational diabetes mellitus (GDM). However, whether these associations are mediated by thyroid hormones and their effect sizes is still unknown. This study aimed to identify the mediating effects of thyroid parameters between prepregnancy body mass index (BMI) or maternal weight gain during early pregnancy on the subsequent risk of GDM.MethodsThis prospective mother-infant cohort study was conducted from 2018 to 2019. A total of 2772 singleton pregnant women were included in the analysis. A questionnaire survey, anthropometric measures, and thyroid function testing were conducted during early pregnancy. Deiodinase activity was evaluated using the free-triiodothyronine-to-free-thyroxine ratio (FT3:FT4). The standard 75-g oral glucose tolerance test was performed during 24 to 28 weeks of gestation to diagnose GDM. A mediation analysis was performed using PROCESS 3.5 to examine the mediating effects of thyroid parameters between prepregnancy BMI or maternal weight gain during early pregnancy on the subsequent risk of GDM.ResultsThe FT3:FT4 ratio was a significant mediator between prepregnancy BMI or maternal weight gain and GDM, accounting for 16.5% and 18.6% of total effects, respectively. FT3 also mediated the association of prepregnancy BMI with GDM, accounting for 3.3% of the total effects. Thyroid-stimulating hormone suppressed the effects of prepregnancy BMI and maternal weight gain on GDM risk, and the proportion of their total effects was 2.4% and 6.4%, respectively.ConclusionDeiodinase activity, as indicated by the FT3:FT4 ratio, was the strongest mediator among thyroid parameters between prepregnancy BMI or maternal early weight gain and GDM.     

Work‐Related Physical Activity Is Not Associated with Body Mass Index and Obesity

Objective: To analyze the association of work‐related physical activity (WRPA) and leisure‐time physical activity (LTPA) with body mass index (BMI) and obesity in the Spanish adult population aged 20 to 60 years. Research Methods and Procedures: The data were taken from the 1993 Spanish National Health Survey. We analyzed a sample of 12,044 men and women representative of the Spanish population aged 20 to 60 years. BMI and frequency of obesity (BMI ≥ 30 kg/m²) were obtained from self‐reported weight and height. Multiple linear regression and logistic regression models were constructed, adjusting for the main confounding factors. WRPA and LTPA were measured by two questions to classify subjects into four categories of physical activity. Results: Neither mean BMI nor percentage of obesity varied significantly (p > 0.05) by WRPA. Mean BMI was significantly higher (p < 0.01) in those who were inactive in their leisure time (25.90 kg/m² in men and 24.43 kg/m² in women) than in those who reported vigorous activity (24.42 kg/m² and 22.97 kg/m² in men and women, respectively). The odds ration (OR) for obesity decreased with increasing level of LTPA in both men (OR of 0.64 for vigorous activity) and women (OR = 0.68), showing a statistically significant dose‐response relation in both men (for linear trend, p = 0.0021) and women (p = 0.0245). Discussion: These results raise questions about the association between WRPA and obesity and suggest the need to reexamine models of the obesity epidemic that point to automation of the workplace as one of the major explanatory factors.     

Lifestyle Interventions Limit Gestational Weight Gain in Women with Overweight or Obesity: LIFE‐Moms Prospective Meta‐Analysis

Objective

This study aimed to evaluate the effects of varied lifestyle intervention programs designed to ameliorate excess gestational weight gain (GWG) in pregnant women with overweight or obesity compared with standard care, including effects on pregnancy outcomes.

Methods

Seven clinical centers conducted separate randomized clinical trials to test different lifestyle intervention strategies to modify GWG in diverse populations. Eligibility criteria, specific outcome measures, and assessment procedures were standardized across trials. The results of the separate trials were combined using an individual‐participant data meta‐analysis.

Results

For the 1,150 women randomized, the percent with excess GWG per week was significantly lower in the intervention group compared with the standard care group (61.8% vs. 75.0%; odds ratio [95% CI]: 0.52 [0.40 to 0.67]). Total GWG from enrollment to 36 weeks' gestation was also lower in the intervention group (8.1 ± 5.2 vs. 9.7 ± 5.4 kg; mean difference: ?1.59 kg [95% CI:?2.18 to ?0.99 kg]). The results from the individual trials were similar. The intervention and standard care groups did not differ in preeclampsia, gestational diabetes, cesarean delivery, or birth weight.

Conclusions

Behavioral lifestyle interventions focusing primarily on diet and physical activity among women with overweight and obesity resulted in a significantly lower proportion of women with excess GWG. This modest beneficial effect was consistent across diverse intervention modalities in a large, racially and socioeconomically diverse US population of pregnant women.

     

Television Viewing Time in Hong Kong Adult Population: Associations with Body Mass Index and Obesity

Background

Obesity is increasing dramatically in the Asia-Pacific region particularly China. The population of Hong Kong was exposed to modernization far earlier than the rest of China, reflecting conditions that are likely to be replicated as other Chinese cities undergo rapid change. This study examined the relationship between television viewing and obesity in a Hong Kong sample. Information about the relationship between a key sedentary behavior, TV viewing, and obesity, and its moderation by demographic characteristics may identify sectors of the population at highest risk for excess weight.

Methods

Data were from Hong Kong Family and Health Information Trends Survey (2009–2010), a population-based survey on the public''s use of media for health information and family communication by telephone interviews with 3,016 Hong Kong adults (age≥18 years). TV viewing time, body mass index (BMI), physical activity and other lifestyle variables were analyzed.

Results

Viewing time was longer in women, increased with age but decreased with education level and vigorous physical activity (all P<0.01). Longer TV viewing time was significantly associated with higher BMI (Coefficients B = 0.17, 95% CI: 0.11, 0.24) after adjusting for age, gender, employment status, marital status, education level, smoking activity and vigorous physical activity. This association was stronger in women than men (Coefficients B: 0.19 versus 0.15) and strongest in those aged 18 to 34 years (Coefficients B = 0.35). Furthermore, an hour increase in daily TV viewing was associated with 10% greater odds of being obese.

Conclusions

A significant socioeconomic gradient in television viewing time was observed. TV viewing time positively associated with BMI and obesity. The TV viewing – BMI associations were strongest in women and young adults, suggesting vulnerable groups to target for obesity prevention by decreasing TV viewing.     

Cross‐Sectional and Longitudinal Associations between Body Mass Index and Marriage‐Related Factors

Objective: To assess the relationship between marriage and obesity. Research Methods and Procedures: Cross‐sectional and longitudinal associations were examined between participant body mass index (BMI), spouse BMI, and participant diet and exercise habits. Results: Spouse and participant BMI and BMI changes over 2 years were significantly associated. Participant BMI was associated with higher consumption of calorie‐dense foods and lower frequency of physical activity. Participants’ eating and exercise habits were only weakly related to spouse BMI. BMI did not predict the likelihood of marriage or divorce. However, marriage was associated with a significant 2‐year weight gain and divorce with a significant 2‐year weight loss. Discussion: The results suggest that spouse similarity in BMI is at least partly due to shared environment. The observed effects of marriage and divorce on weight may be due to the influence of marriage on inducements to eat (e.g., shared meals) or on motivation for weight control.     

Association of a Body Mass Index Genetic Risk Score with Growth throughout Childhood and Adolescence

Background

While the number of established genetic variants associated with adult body mass index (BMI) is growing, the relationships between these variants and growth during childhood are yet to be fully characterised. We examined the association between validated adult BMI associated single nucleotide polymorphisms (SNPs) and growth trajectories across childhood. We investigated the timing of onset of the genetic effect and whether it was sex specific.

Methods

Children from the ALSPAC and Raine birth cohorts were used for analysis (n = 9,328). Genotype data from 32 adult BMI associated SNPs were investigated individually and as an allelic score. Linear mixed effects models with smoothing splines were used for longitudinal modelling of the growth parameters and measures of adiposity peak and rebound were derived.

Results

The allelic score was associated with BMI growth throughout childhood, explaining 0.58% of the total variance in BMI in females and 0.44% in males. The allelic score was associated with higher BMI at the adiposity peak (females  =  0.0163 kg/m² per allele, males  =  0.0123 kg/m² per allele) and earlier age (-0.0362 years per allele in males and females) and higher BMI (0.0332 kg/m² per allele in females and 0.0364 kg/m² per allele in males) at the adiposity rebound. No gene:sex interactions were detected for BMI growth.

Conclusions

This study suggests that known adult genetic determinants of BMI have observable effects on growth from early childhood, and is consistent with the hypothesis that genetic determinants of adult susceptibility to obesity act from early childhood and develop over the life course.     

Trends in Parent-Child Correlations of Childhood Body Mass Index during the Development of the Obesity Epidemic

Background

The intergenerational resemblance in body mass index may have increased during the development of the obesity epidemic due to changes in environment and/or expression of genetic predisposition.

Objectives

This study investigates trends in intergenerational correlations of childhood body mass index (BMI; kg/m²) during the emergence of the obesity epidemic.

Methods

The study population was derived from the Copenhagen School Health Records Register, which includes height and weight measurements since birth year 1930. Mothers and fathers with BMIs available at ages 7 (n = 25,923 and n = 20,972) or 13 years (n = 26,750 and n = 21,397), respectively, were linked through the civil registration system introduced in 1968 to their children with BMIs available at age 7 years. Age- and sex-specific BMI z-scores were calculated. Correlations were estimated across eight intervals of child birth years (1952–1989) separately by sex. Trends in these correlations were examined. Whereas the mother-child correlations reflected the biological relationship, a likely decline in the assignment of non-biological fathers through the registration system across time must be considered when interpreting the father-child correlations.

Results

The BMI correlations between mothers and sons ranged from 0.29–0.36 and they decreased marginally, albeit significantly across time at ages 7–7 years (−0.002/year, p = 0.006), whereas those at 13–7 years remained stable (<0.0004/year, p = 0.96). Mother-daughter correlations ranged from 0.30–0.34, and they were stable at ages 7–7 years (0.0001/year, p = 0.84) and at 13–7 years (0.0004/year, p = 0.56). In contrast, father-son correlations increased significantly during this period, both at ages 7–7 (0.002/year, p = 0.007) and at ages 13–7 years (0.003/year, p<0.001), whereas the increase in father-daughter correlations were insignificant both at ages 7–7 (0.001/year, p = 0.37) and at ages 13–7 years (0.001/year, p = 0.18).

Conclusion

During the obesity epidemics development, the intergenerational resemblance with mothers remained stable, whereas the father-child BMI resemblance increased, possibly reflecting changes in family relationships, and unlikely to have influenced the epidemic.     

The Relationship of Rapid Weight Gain in Infancy to Obesity and Skeletal Maturity in Childhood

Objective: Children with birth weight appropriate for gestational age (AGA) who also demonstrate rapid weight gain in infancy have a greater risk of being overweight or obese during childhood. A concurrent advancement in skeletal maturity would account for their greater size and would, therefore, not necessarily pose a threat of greater risk during adolescence and early adulthood. This study aims to determine whether children with rapid weight gain during infancy have advanced skeletal maturity during childhood. Research Methods and Procedures: One hundred and ninety‐three African children (boys = 108; girls = 85) of normal birth weight and gestational age were assessed from birth to 9 years. Body composition was assessed at 9 years of age by whole‐body DXA, and skeletal maturity was assessed using the Tanner‐Whitehouse II technique. Rapid weight gain in infancy was defined as a +0.67 change in weight‐for‐age Z‐score between birth and 2 years. Results: Rapid weight gain was experienced by over 20% of the sample. Children with rapid weight gain were significantly lighter at birth and significantly taller, heavier, and fatter throughout childhood. Chronological age and Tanner‐Whitehouse II technique skeletal ages at 9 years were not significantly different between groups or between sexes within groups. Discussion: Because AGA children with rapid weight gain have a greater risk of overweight and obesity but are not advanced in skeletal maturity, later adolescent adjustments toward average weight and fatness values are unlikely. The identification and monitoring of such children is of importance in reducing their risk of morbidity.     

Obesity and Physical and Emotional Well‐Being: Associations between Body Mass Index,Chronic Illness,and the Physical and Mental Components of the SF‐36 Questionnaire

Objective: To clarify the associations between obesity and health‐related quality of life by exploring the associations between physical and emotional well‐being in relation to obesity and the presence of other chronic illness. Research Methods and Procedures: The study data were collected as part of a postal‐survey within the old Oxford Regional Health Authority of England in 1997. Completed questionnaires were returned by 8889 of 13,800 randomly selected adults aged 18 to 64 years. The main outcome measures were body mass index in five categories (underweight, normal weight, overweight, moderately obese, morbidly obese); chronic illness status (any vs. none and number of such illnesses 0, 1 to 2, 3+); and mean SF‐36 questionnaire score in two summary component measures reflecting physical and emotional well‐being. Results: Of the subjects, 31% were overweight and an additional 11% were obese. Body mass index was significantly associated with health status, but the pattern varied according to whether the measure reflected physical or emotional well‐being. Physical, but not emotional, well‐being deteriorated markedly with increasing degree of overweight and was limited in subjects who were obese but had no other chronic condition; subjects with chronic illnesses other than obesity were compromised in both dimensions. In terms of the number of chronic illnesses reported, the additional presence of obesity was associated with a significant deterioration in physical but not emotional well‐being. Discussion: Overweight and obesity are associated with poor levels of subjective health status, particularly in terms of physical well‐being. The limitations in emotional well‐being that are reported here and in other studies may be a result of confounding by the presence of accompanying chronic illness.     

妊娠期糖尿病孕妇产前体质量指数对分娩方式和新生儿体重的影响

目的：分析妊娠期糖尿病（GDM）孕妇产前体质量（BMI）指数对分娩方式及新生儿体重的影响。方法：收集2010年5月至2012年5月于我院产科分娩的GDM孕妇资料,共117例,按照BMl分级标准将所有产妇分为低体重组（18例）、正常体重组（65例）、超体重组（21例）、肥胖组（13例）,比较四组产妇分娩方式及新生儿出生体重。结果：低体重组、正常体重组顺产率分别为55．56％、61．54％,明显高于超体重组38．10％、肥胖组15．38％（X2=11．035,P=0．012）;而肥胖组剖宫产率85．62％K高于超体重组61．90％,比较差异具有统计学意义（P〈0．05）。低体重组、正常体重组新生儿巨大儿发生率分别为5．56％、9．23％,低于超体重组33．33％、肥胖组46．15％,差异具有统计学意义（P〈0．05）。结论：GDM孕前BMI与孕妇妊娠结局密切相关,孕前积极检查,将BMI控制在25以下,可有效降低剖宫产率及巨大儿的发生率。     

Associations of Aging and Birth Cohort with Body Mass Index in a Biethnic Cohort

Objective: To examine associations of aging and birth cohort with body mass index (BMI) in a biethnic cohort. Research Methods and Procedures: This was a longitudinal closed cohort study of 14, 500 white and African‐American men and women, 45 to 64 years of age, followed for 9 years. Aging was defined as the length of the interval in years between baseline and following visits. Birth cohort was defined by the year in which participants were born. Mixed model analyses were used to examine associations of aging, birth cohort, and BMI in four ethnicity‐gender groups. Results: We found that aging was associated with an increase in BMI in white and African‐American men and women. The associations between aging and BMI were stronger in the younger birth cohorts. Except for white women, younger birth cohort was associated with a higher BMI. After adjusting for aging, birth cohort was associated with an increase in BMI of 0.1 kg/m² [95% confidence interval (95% CI): ?0.1, 0.3] among white women. The corresponding values for African‐American women, white men, and African‐American men are 0.5 kg/m² (95% CI: 0.1, 0.9), 0.6 kg/m² (95% CI: 0.4, 0.8), and 0.6 kg/m² (95% CI: 0.2, 1.0), respectively. Discussion: Our analyses show that, in all except white women, people in this age range who were born later have a higher BMI at the same attained age. In all groups, people who are born later gained more weight as they aged. In general, subjects ages 45 to 64 years gained weight as they aged 9 years.     

The Relationship between Body Mass Index and Post-Cessation Weight Gain in the Year after Quitting Smoking: A Cross-Sectional Study

Introduction

There is wide variability in the amount of weight gained when quitting smoking, but little is known about key predictors of weight gain. We examined the impact of body mass index (BMI) category and sociodemographic variables on post-cessation weight gain.

Materials and Methods

We utilized National Health and Nutrition Examination Survey data from five consecutive cycles of data collection from 2003–2004 to 2011–2012 to estimate post-cessation weight gain by BMI category among recent quitters (n = 654). We analyzed data on their “current weight” and their “past year weight”. We also compared the recent quitters with current smokers, in order to estimate the amount of weight that could be attributed to quitting smoking.

Results

Recent quitters gained 1.4 kg (95% CI: 0.8 to 2.0), while current smokers had a non-significant weight change (-0.01 kg (95% CI: -0.3 to 0.2). Weight gain was significant for those in the normal weight (3.1 kg, 95% CI: 2.3 to 3.9) and overweight BMI categories (2.2 kg, 95% CI: 1.1 to 3.2).

Conclusions

BMI category is a key factor in the extent of post-cessation weight gain, with normal and overweight recent quitters gaining significant amounts of weight.