The care of infants with rapid weight gain: Should we be doing more?

Abstract

Rapid weight gain (RWG) during infancy is a known risk factor for later childhood obesity. It can be measured using a range of definitions across various time periods in the first 2 years of life. In recent years, some early childhood obesity prevention trials have included a focus on preventing RWG during infancy, with modest success. Overall, RWG during infancy remains common, yet little work has examined whether infants with this growth pattern should receive additional care when it is identified in health‐care settings. In this viewpoint, we contend that RWG during infancy should be routinely screened for in health‐care settings, and when identified, viewed as an opportunity for health‐care professionals to instigate non‐stigmatising discussions with families about RWG and general healthy practices for their infants. If families wish to engage, we suggest that six topics from early life obesity prevention studies (breastfeeding, formula feeding, complementary feeding, sleep, responsive parenting, and education around growth charts and monitoring) could form the foundations of conversations to help them establish and maintain healthy habits to support their infant's health and well‐being and potentially lower the risk of later obesity. However, further work is needed to develop definitive guidelines in this area, and to address other gaps in the literature, such as the current lack of a standardised definition for RWG during infancy and a clear understanding of the time points over which it should be measured.

Rapid weight gain (RWG) during infancy has consistently been identified as a major risk factor for later childhood obesity. ¹ , ² Although there are inconsistencies in how RWG during infancy is defined, the prevalence has been estimated as 18–35% in several studies, ³ , ⁴ , ⁵ , ⁶ , ⁷ with others suggesting higher figures of almost 50% of infants. ⁸ , ⁹ Regardless of the variation observed, these figures indicate that RWG during infancy is common. While it has been included as an outcome of interest in several early life trials which have focused on infancy as a critical period for the prevention of later obesity, ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ to date research does not appear to have investigated whether infants with identified RWG, and their families, would benefit from additional care designed to support the infant's overall health and well‐being and potentially reduce their risk of becoming obese in later childhood. Detailed guidelines for health‐care professionals to follow when working with the families of infants with RWG do not yet exist, although qualitative work has indicated that they would be valued. ¹⁵ , ¹⁶

In this viewpoint, we explore the literature on RWG during infancy, and consider how infants with identified RWG, and their families, could be supported to establish and maintain practices which will support the infant's overall health and well‐being, while also potentially reducing their risk of later obesity. We also describe several existing gaps in the literature which ideally need to be resolved before the introduction of any routine care for families with infants experiencing RWG.

First Steps

If specific care is to be routinely provided to infants with RWG, then such infants must be easily identifiable within health‐care settings. At present, identification is complicated by the lack of a standardised definition and time‐frame/s over which weight gain should be assessed. In the paediatric literature, RWG during infancy is most frequently defined as an increase in weight‐for‐age z‐score (WAZ) of ≥0.67 standard deviations (SD) between two time points somewhere in the first 2 years of life, with limited consistency in the time gap between measures. ¹⁷ , ¹⁸ However, conditional weight gain scores, ¹⁹ , ²⁰ or measurements of weight adjusted for length, such as an increase in weight‐for‐length z‐score, ²¹ , ²² or body mass index (BMI) z‐score ²³ (often also using a difference of ≥0.67 SD between two time points) have also been used. In some cases, RWG has been described as the upwards crossing of two or more centile lines on WAZ ²⁴ or weight‐for‐length growth charts. ²⁵ , ²⁶ Importantly, the magnitude of change indicated by the upwards crossing of two centile lines will be influenced by which growth charts are used. Some (such as the UK‐World Health Organisation (WHO) ²⁷ and New Zealand‐WHO growth charts ²⁸ ) have 9 centile lines which are each spaced 0.67 SD of a z‐score apart, while others (such as the Centers for Disease Control charts ²⁹ ) have 7 major centile lines which are not uniformly spaced 0.67 SD apart. Furthermore, the trajectories displayed on growth charts reflect the populations whose measurements were used in their development. The WHO growth charts are based on an international sample of healthy breastfed infants of non‐smoking mothers; essentially, they are a growth standard describing how healthy children should grow under optimal conditions. ³⁰ In comparison, the Centers for Disease Control charts are a growth reference based on the results of five nationally representative samples from the USA between 1963 and 1994; relatively few of the infants in those samples were breastfed for more than a few months. ³¹ Health‐care professionals should be aware of which growth charts they are using, the populations on whom they were based, and how infants in their care with RWG compare to those populations.

Growth charts can also be used for identifying children who are overweight or obese. For children aged <5 years, WHO define overweight as weight‐for‐height greater than 2 SD, and obesity as weight‐for‐height greater than 3 SD, above the WHO Child Growth Standards median. ³² It is important that health‐care professionals understand that the definition of RWG during infancy is distinct from the definitions of overweight and obesity, and that the two conditions do not necessarily overlap.

RWG has been reported to occur across a range of time periods during infancy. ⁸ , ¹⁷ In the literature, an infant's birthweight often forms the first measure, while the second measure may be taken as little as 3–4 months, ⁸ , ³³ , ³⁴ or as much as 24 months ³ later. The different time periods mean that caution is required when comparing study results, as RWG over a shorter interval during infancy may be indicative of a much faster overall growth rate than RWG over a longer interval. The risk of later obesity may vary depending on the time period over which RWG occurs; for example, one systematic review found that RWG from birth to 1 year was associated with higher odds of overweight or obesity in later childhood than RWG from birth to 2 years. ¹⁷ Direct comparison of the relative impact of all the different time points utilised in the literature on later obesity risk does not appear to have occurred. Additionally, the time frames used to assess RWG in health care may differ from those used in research, and are potentially context dependent. For example, RWG during infancy may be observed between two routine Well Child checks, ³⁵ or while an infant is being specifically monitored for other reasons. If possible, standardisation of both the definition and time‐frame/s over which RWG is measured in health‐care settings would be useful so that RWG during infancy can be easily screened for, and consistently identified. This forms the first of our recommendations for research priorities for the care of infants with RWG, which are outlined in Table 1. Once this has been achieved, electronic health records (which are increasingly used in health‐care settings) ³⁶ could be programmed to automatically identify whether RWG has occurred in an infant, and to flag such occurrences to health‐care professionals.

Table 1.

Suggested research priorities for the care of infants with rapid weight gain (RWG) in health‐care settings

1.	Decide upon a standardised definition for RWG including the ideal time frame/s during infancy over which it should be measured, so that this can consistently be applied in health‐care settings.
2.	Identify which topics and related messages should form the basis of strategies for the care of infants with RWG.
3.	Determine how to effectively engage with diverse groups using sensitive and culturally relevant approaches to the topics identified in (2) above.
4.	Develop and test strategies designed to care for infants with RWG. If possible, examine the impact of these strategies on children's overall health and well‐being, as well as on their risk of later childhood obesity.
5.	Use the results of 1, 2, 3 and 4 above to develop evidence‐based guidelines for the care of infants with RWG in health‐care settings.

Can Research about Risk Factors Inform Care?

The factors which contribute to RWG during infancy are complex and multi‐factorial. ¹⁶ A recent pooled analysis of data from seven Australian and New Zealand cohorts (total n = 4542) undertook univariate and multivariate analyses of the determinants of RWG during infancy (defined as a gain in WAZ of ≥0.67 SD between birth and 1 year of age ³⁷ ). The multivariate analyses recognised that some factors (e.g. infant birthweight) may underlie the causal pathways between other factors (e.g. maternal smoking) and RWG during infancy. ³⁷ They found that male infants (compared to female infants), and infants of women who were born in Australia or New Zealand (compared to infants of women who were born elsewhere) were at increased risk, while infants of higher birthweight (compared to lower birthweight), greater gestational age (compared to younger gestational age), and those who were breastfed for ≥6 months (compared to those who were breastfed for <6 months) were at lower risk of RWG. ³⁷ In univariate analyses, maternal smoking (compared to no maternal smoking) was associated with increased risk, while introduction of solid foods at ≥6 months of age (compared to introduction of solids at <6 months of age) and having siblings (compared to not having siblings) were associated with reduced risk. However, these associations were attenuated in multivariate analyses. No association with maternal age, education, marital status or pre‐pregnancy BMI was observed. ³⁷ Studies from outside Australia and New Zealand have generally reported similar results, especially with regard to the apparent protective effects of breastfeeding (compared to formula feeding), ³ , ⁷ , ⁸ , ³⁸ , ³⁹ higher (compared to lower) infant birthweight ⁷ , ⁸ , ⁴⁰ or BMI, ³ and older (compared to younger) gestational age at birth, ³ , ⁵ , ⁶ , ⁷ and with the increased risk associated with maternal smoking during pregnancy ⁵ , ⁶ , ⁴⁰ , ⁴¹ and being a first‐born child. ³ , ⁵ , ⁷ However, not all findings are consistent. For example, having a migrant background was associated with an increased risk of RWG in a German study, ⁶ which contrasts with the findings of the Australasian pooled analysis. ³⁷ A range of other risk factors that have been described might be useful to consider but have been infrequently measured between studies, and interventions based on these risk factors require further research to be better understood. ⁴ , ⁴² , ⁴³ , ⁴⁴ It is notable that while the impact of demographic factors on risk of RWG has frequently been described, there is a paucity of research describing the impact of various psychosocial factors (such as maternal mental health). Future work could aim to investigate these.

Can Early Life Obesity Prevention Interventions Inform Care of Infants with RWG?

Several trials have investigated whether intervening during infancy is an effective strategy for the prevention of obesity in later childhood. ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ While some of these trials have measured RWG in infancy as an outcome, in most cases their interventions have been designed to prevent later obesity in general, rather than to directly influence RWG during infancy. ²⁰ , ²³ , ⁴⁵ , ⁴⁶ , ⁴⁷ They have typically recruited mothers antenatally ¹² or within the new‐born period. ¹⁰ , ¹¹ , ¹³ , ¹⁴ Their intervention content has usually been focused on the provision of anticipatory guidance to help families establish healthy practices around behaviours known to be associated with obesity (such as feeding, sleep and activity) on the premise that it is easier to establish healthy practices early in life, than to change less healthy practices later. Results from the limited literature to date suggest only modest success in preventing RWG during infancy. ²⁰ , ²³ , ⁴⁵ , ⁴⁶ , ⁴⁷ Despite these limitations, it may still be useful to look to the interventions of these trials to identify whether some of their content could be transferable to the care of infants with RWG. This is especially pertinent because to date, there do not appear to have been any randomised controlled trials which have identified infants with RWG and randomised them to an intervention or usual care/control group to investigate whether it is possible to intervene on established RWG and reduce the subsequent risk of childhood obesity. Such interventions could possibly be considered inappropriate or stigmatising by some families. In at least one study, mothers have expressed the viewpoint that infancy is too early to intervene to prevent obesity ⁴⁸ while other work has identified a ‘common belief’ among parents that heavier babies are healthier. ⁴⁹ Thus, there is a need to consider whether structured interventions with a goal of reducing later childhood obesity are necessary for infants with RWG, or whether it would be more appropriate to provide them and their families with specific care which is aimed at supporting the infant's overall health and well‐being and which may or may not have a secondary effect of helping prevent later overweight or obesity.

Our examination of the intervention content of obesity prevention trials, and consideration of whether it could be applied in health‐care settings for the care of infants with RWG, suggested that while some of that content may be useful, there are some key differences between the two approaches. Prevention interventions may start during pregnancy, or even pre‐conception, and can theoretically target almost all of the most common risk factors for RWG during infancy. Zheng et al. suggested that preventive strategies for RWG during infancy could focus on helping women (especially primigravid women) to deliver full‐term infants with healthy birth weights, through practices such as supporting women to abstain from smoking while pregnant. ³⁷ In comparison, the pool of topics which can be addressed later, once an infant has been identified as having RWG at some point in the first 2 years of life, are smaller. We identified six key topics from obesity prevention interventions which could potentially be useful: breastfeeding, formula feeding, complementary feeding, infant sleep, responsive parenting practices, and education around growth charts and growth monitoring. These have been briefly outlined in Table 2, where the authors have included some potential guidelines related to each of the topics. They are based on existing knowledge and guidelines from a range of reliable sources (such as the WHO and national health ministries) and thus the messages themselves are not particularly novel, but the grouping of these topics together for consideration in the context of RWG during infancy is new. We have demonstrated how health‐care professionals could potentially incorporate these topics in their work with families of infants with RWG using a hypothetical case study (see Table 3). However, we also emphasise that the suggested topics must be considered cautiously and critically by readers, and that more research and further content development is necessary before definitive recommendations can be made.

Table 2.

Potential topics to discuss with families of infants with rapid weight gain (RWG)

1.	Breastfeeding When RWG is identified in an infant who is breastfed: Continue to encourage breastfeeding in accordance with World Health Organization guidelines (exclusive breastfeeding to 6 months and continued breastfeeding alongside complementary foods to age 2 or beyond). 59 Emphasise that breastfeeding has many benefits for mother and baby and that RWG is not a reason to stop breastfeeding. Identify if feeding is being offered for non‐hunger reasons (comfort, bonding, crying) and consider other strategies for these.
2.	Formula feeding When RWG is identified in an infant who is formula fed: Support best practice formula feeding 60 in a non‐judgemental manner. Assess formula feeding intake to determine whether changes should be made to the type of formula, concentration and volume being consumed by the infant. 60 Encourage the use of responsive formula feeding practices, including responsiveness to infant hunger and satiety cues. 46 Suggest avoiding or limiting reliance on cues which are external to the infant, such as how much formula has been consumed or whether the bottle is empty.
3.	Complementary feeding practices When an infant is identified as having RWG: Consider their age and whether they have started having complementary foods, or fluids other than milk or water. If the infant is yet to start solids, the family should be encouraged to wait until the infant is 6 months old. If the infant is >6 months old, or is <6 months old but has commenced solid foods, they should be fed in accordance with current national infant nutrition guidelines. 61
4.	Sleep When an infant is identified as having RWG: Discuss the infant's sleep with parents and caregivers, and provide families with support and advice to help their infant sleep well. 62
5.	Responsive parenting practices When an infant is identified as having RWG: Help families to embed responsive practices across all domains of parenting, including breastfeeding, formula feeding, complementary feeding and infant sleep. Explain that being responsive involves reacting to an infant's needs in a prompt and developmentally appropriate way. 63
6.	Education around growth charts and growth monitoring, and why they are important When an infant is identified as having RWG: Use growth charts to help explain RWG during infancy to families. Explain that RWG during infancy is both common, and associated with an increased risk of later childhood obesity. This does not mean that all infants who have RWG will become overweight or obese. However, when it is identified, families should be offered extra guidance to help them set up and maintain habits which will support the health of their infant as they move into childhood and beyond. Use the growth charts in ongoing monitoring to display the pattern of growth.

Table 3.

A case study of an infant with rapid weight gain (RWG)

Scenario: You are seeing Emily and her mother Sarah for a routine well child visit. You last saw them when Emily was 5 months old, and she is now 9 months old. At the beginning of the visit, you weigh and measure Emily, and enter her measurements into her electronic health record, which includes growth charts for weight and length. It automatically compares today's measurements with those from her 5‐month visit and shows that her weight centile has moved from the 60th (corresponding z‐score of +0.5 SD), to the 90th centile (corresponding z‐score of +1.3 SD, and demonstrates a change in weight z‐score of +0.8 SD between the two time points). Emily's length has also increased but is on the same centile line (50th) as at the 5‐month visit. You know that RWG during infancy is a risk factor for later childhood obesity and that it might be timely to initiate a discussion about this with Sarah today. Further background: Sarah was unable to breastfeed, so Emily has been formula fed since birth. Emily was just starting on complementary foods when you last saw her. There were no concerns about any aspect of Emily's health at that point. Today, Emily seems well, her development is otherwise normal, and it is evident that she has a good bond with her mother.

What questions could you ask?

Ask permission to discuss Emily's overall growth with Sarah. Sarah, is it ok if we talk about Emily's growth today? Only proceed to (2) if Sarah answers in the affirmative. Use Emily's electronic health record, including growth charts, to show that while her length is increasing along the 50th centile, her weight has increased more rapidly. Explain that this pattern of weight gain has been linked with overweight in later childhood. Suggest that if Sarah wishes, you can talk with her about some day‐to‐day activities which may need modification to support Emily's overall health and well‐being as she grows. Precede each topic with a question asking whether Sarah would like to discuss it: 3 Formula feeding and complementary feeding: discuss Emily's current intake of both formula and solid foods. How do these intakes, and the feeding practices surrounding them, align with current healthy eating guidelines for babies and toddlers? 61 Consider: Formula: What type is being used and is it being made up to the correct concentration? What volume does Emily consume each day, and are responsive bottle feeding practices 61 being followed? Food: What foods are being offered, and in what quantities? Are they age‐ and developmentally appropriate, and is Emily on a progression towards eating family foods by the time she is 12 months of age? 61 Is Emily offered any drinks other than water? Both: How is Emily's intake of food spaced around her formula intake, and throughout the day/night? Are Sarah and other family members aware of, and able to interpret and respond to, hunger and satiety cues 61 from Emily? 4 Sleep: Explain that sleep plays a role in growth and health which is sometimes overlooked. Consider Emily's current sleep routine – how does it align with sleep guidelines 64 for infants? Is there anything that Sarah, or other caregivers, can do to support Emily's sleep? It may be useful to direct Sarah to online sleep resources such as babysleep.com. 65 5 Responsive parenting practices: Explain that this means being responsive to Emily's needs by looking out for, and responding, to her cues with regards to needing food, sleep and opportunities for play, including active play. 66 Are there any specific situations where Sarah could respond differently to Emily's needs?

What will you do next?

Sarah's reactions and answers to the above questions should be used as a guide for you to advise on options in each area and agree on a plan to support Emily's health and well‐being.

Strategies for caring for infants with RWG need to be tailored to the infant's age and developmental stage, and to existing life‐style behaviours within their family. For example, mothers of infants with RWG who have stopped breastfeeding are unlikely to be able to start again when RWG is identified, so strategies for them should focus on other topics. Other practices, such as the over‐feeding of infant formula ⁵⁰ may be difficult for parents and caregivers to reverse at the point in time when RWG is identified, especially if they have become well‐established over a period of weeks or months. Thus, extra levels of support which may not be necessary in some RWG prevention initiatives may be essential when providing care for infants with RWG and their families.

What Else Needs to be Considered in the Care of Infants with RWG?

In addition to considering which topics should be included in guidelines for the care of infants with RWG, consideration also needs to be given to how these topics are broached with families. Weight can be a complex, emotionally charged topic for adults to communicate about ⁵¹ and this could be amplified in discussions about RWG in an infant. It is important that health‐care providers are able to explain to families that although RWG during infancy is a risk factor for later childhood obesity, not all infants with RWG will go on to become children who are classified as overweight or obese. Health‐care providers should also be aware that families will react differently to conversations about the risk of future obesity. This was demonstrated in a New Zealand study where the acceptability of early childhood obesity prediction models was tested with diverse families through an online questionnaire. ⁵² Nearly two‐thirds of caregivers were found to be very receptive to hypothetical risk communication about their child's obesity risk, information, although it was frequently reported that they would also feel ‘worried’ or ‘upset’ if they were told that their infant was at risk of childhood obesity. ⁵² The remaining one third of caregivers reported that they would ‘maybe’ (19%), ‘probably not’ (13.5%) or ‘definitely not’ (5.4%) be receptive to the information provided. Parents and caregivers of infants with RWG might have similar responses. Thus, it may be appropriate for health‐care providers to use a multiple‐step process to first determine if the family of an infant with identified RWG are interested in talking about it further, and in discussing practices which will support the child's overall health and well‐being. If families are receptive, then it is important to consider how information can be provided in a sensitive manner which encourages effective collaboration between families and health‐care professionals.

Where Else Can Health‐Care Professionals Look for Guidance?

In the absence of specific guidelines for the care of infants with RWG, obesity management guidelines may be a useful place to look for principles which could be broadly transferable. In their clinical practice guideline for obesity in adults, Obesity Canada has emphasised the need for health‐care professionals to focus on patient‐centred health and well‐being outcomes (rather than weight alone) and to reduce the pervasive weight bias and stigma experienced by people with obesity. ⁵³ Focusing on the topics in Table 2, and how they could be modified to positively influence an infant's overall health and well‐being, is likely to be more appropriate and acceptable to parents than discussions which focus on the long‐term risks of RWG or on risk factors which were present during pregnancy or at birth and which cannot be modified at the time that RWG is identified. The Canadian adult obesity guidelines present the ‘5A's’ for the ‘Patient Journey in Obesity Management’. ⁵³ These have also been incorporated into a toolkit for managing paediatric obesity in primary care in Canada, ⁵⁴ and they provide a useful framework for health professionals to refer to when working with the families of infants with RWG. The first of the 5A's is ‘Ask Permission’ which refers to health professionals asking permission to discuss a patient's weight and to offer advice and treatment options. Further discussions should only ensue if the patient gives their permission. This approach shows compassion and empathy and builds patient‐provider trust. ⁵³ Such a philosophy could be transferred to the care of RWG in infants, whereby parents and caregivers of infants with RWG would be asked to consent to the health‐care professional discussing their infant's RWG with them. If the family agreed, progression through the rest of the 5A pathway (Assess their story, Advise on management, Agree on goals, and Assist with drivers and barriers) ⁵³ could commence.

Obesity management guidelines recognise that some groups are over‐represented in obesity statistics, and acknowledge that health professionals must be aware of cultural diversity, and able to engage with people of different backgrounds. ⁵⁵ , ⁵⁶ To date, most early life obesity prevention interventions which have measured RWG during infancy have been conducted predominantly in ‘White’ or ‘European’ and socially advantaged populations. ²⁰ , ⁴⁵ , ⁴⁶ , ⁵⁷ However, the responsive parenting intervention included in one recent trial ⁴⁷ was a version of an intervention from an earlier trial ¹¹ , ²⁰ which had been adapted for an African‐American population. The adapted intervention had smaller, non‐significant effects in the African‐American population ⁴⁷ relative to the earlier version which was tested in a predominantly white sample. ²⁰ This indicates that the same, or similar, interventions for RWG during infancy may have different outcomes in different population groups. This should be carefully considered in future research to ensure that new initiatives do not contribute to health inequities. ⁵⁸

Conclusion

Research and practice in the area of RWG during infancy is complicated by the lack of a standardised definition and time‐frame/s over which to measure it. These are needed if RWG during infancy is to be consistently identified and addressed in health‐care settings. Regardless of the definition used, RWG is a common risk factor for later childhood obesity, yet to date, very little research has considered whether families of infants with RWG should be provided with specific care to support their infants' overall health and well‐being, while also potentially reducing the risk of later childhood obesity. This viewpoint article identified six topics from early childhood obesity prevention trials (breastfeeding, formula feeding, complementary feeding, sleep, responsive parenting, and growth chart education and monitoring) which could be included in future approaches to caring for infants with RWG. Further work is needed to refine these topics and include them in future guidelines for health professionals about the care of infants with RWG. Such guidelines should also include information on how to provide care for these infants and their families in culturally responsive, non‐stigmatising ways. While it is currently difficult to predict whether increased provision of care for infants with RWG would have a direct impact on the risk of childhood obesity, increased care offers an opportunity to improve the short‐ and long‐term health and well‐being of infants with this growth pattern and is thus a worthwhile topic for further investigation.