Introduction

“Losing the baby weight” may seem like an undue societal pressure for a person who has recently given birth to then seamlessly return to their pre-baby weight. There are, however, numerous health concerns associated with postpartum weight retention (PPWR) on future pregnancies and the long-term health of the birthing person-infant dyad.

Postpartum weight retention refers to the weight retained after giving birth compared to prepregnancy weight. In the US, a significant portion of women and birthing people experience PPWR. Studies show that 50–75% of patients weigh more than their prepregnancy weight at 12 months postpartum with half retaining at least 10 pounds and a quarter at least 20 pounds [1, 2]. Furthermore, those with PPWR tend to weigh on average 15 pounds more at 2 years after delivery compared to prepregnancy [3]. Among those with prepregnancy obesity, about 50% still experience PPWR at 6 months postpartum, and this risk increases if gestational weight gain exceeded recommended levels [4].

Several factors increase the likelihood of PPWR exceeding 20 pounds, including race/ethnicity (African American or Hispanic), age < 30 at delivery, public insurance, lower physical activity levels, job loss during pregnancy, and exceeding gestational weight gain recommendations [1, 3]. Cesarean delivery is also associated with PPWR as patients who have a cesarean birth are 30% more likely to retain at least 10 pounds at 1 year postpartum than those who deliver vaginally [2]. According to a focus group of postpartum patients receiving Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) benefits in Southern California, additional barriers to weight loss after delivery include lack of knowledge, time, child care, and self-efficacy (belief in one’s own ability to execute necessary steps to achieve a desired goal) [5]. Other contributors include postpartum depression and the 40-day rule (a cultural belief that the mother must rest for 40 days following birth, including avoidance of household chores or care of other children) [5]. The same study found that motivators for postpartum weight loss included modeling healthy behavior for children and fear of developing chronic illness [5].

PPWR affects the outcomes of future pregnancies. Patients whose BMI is at least 2–3 kg/m2 BMI units greater in a successive pregnancy than the previous pregnancy are more likely to develop hypertensive disorders of pregnancy, gestational diabetes, have large for gestational age infants, require cesarean delivery, and experience stillbirth, even if they remain in a normal BMI category [6,7,8,9]. For patients whose PPWR results in obesity (BMI ≥ 30 kg/m2), there are additional potential complications which include spontaneous abortion, congenital malformation, obstructive sleep apnea, carpal tunnel syndrome, endometritis, and venous thrombosis [10]. Patients with obesity who lose weight between pregnancies (starting weight lower in successive pregnancy than the index pregnancy) have a 30% reduction in the risk of a large for gestational age infant; the effect of weight loss on decreasing other adverse obstetric outcomes is less clear [11].

Postpartum weight retention is also associated with an increased risk for long-term cardiovascular disease. A large Danish population-based study demonstrated that patients whose weight was at least 1 kg/m2 BMI unit higher than their prepregnancy weight were 25% more likely to develop chronic hypertension by 18 months postpartum [12]. For patients with normal or underweight prepregnancy BMI and a PPWR of at least 2 kg/m2 BMI units at 18 months postpartum, they were 50% more likely to have cardiovascular disease diagnosed [12]. Regarding the offspring’s health, a child of a patient with an interpregnancy weight gain of at least 3 kg/m2 BMI units is almost 20% more likely to be overweight or obese at 4–5 years of age [13].

Given the potential health impacts of postpartum weight retention, supporting mothers in their weight loss goals is crucial for both their well-being and that of their children. While there is no single best approach, this review will explore the evidence for various strategies that include counseling and resources.

Physiologic Weight Loss

Independent of the balance between caloric intake and energy expenditure, there is an expected baseline weight gain (or in some, weight redistribution) due to several physiologic changes of pregnancy. The uterus hypertrophies (averaging 2 pounds at term), blood volume and extravascular fluid volume increase (adding 5 to 7 pounds), breasts enlarge (1 to 3 pounds), and there is the weight contribution from the products of conception themselves (7 to 8 pounds for the fetus, 2 pounds of amniotic fluid, and 1 to 2 pounds of placenta) [14]. Therefore, postpartum weight loss intuitively begins immediately following parturition with the expulsion of the fetus, placenta, and amniotic fluid. Uterine involution, loss of lochia, and postnatal diuresis lead to the loss of an additional 5 to 15 pounds, with the majority of physiologic weight loss happening in the first 6 weeks postpartum [15].

Exercise

When combined with caloric restriction, regular physical activity reduces PPWR. In a comprehensive meta-analysis by Dodd, et al., 27 randomized-controlled trials comparing postpartum weight change in patients enrolled in a lifestyle intervention (dietary instruction, exercise regimen, or both) versus standard care were evaluated [16]. An average weight loss of 4 pounds and 3 pounds was seen in trials with dietary intervention alone (N = 75) and physical activity intervention alone (N = 93), respectively. However, in trials with combined diet and exercise interventions (N = 1156), the average postpartum weight loss seen was 5.5 pounds in all-comers and 6 pounds in patients who were overweight or obese at the start of the index pregnancy (N = 667). Patients with combined diet and exercise instruction were also more likely to maintain their weight loss at 12 months post-delivery than control groups [16].

Avoiding a sedentary lifestyle and engaging in regular physical activity are recommended for most patients in the postpartum period [17]. Guidance from the U.S Department of Health and Human Services and the World Health Organization advise postpartum patients to engage in at least 150 min of moderate-intensity aerobic exercise per week, spread throughout the week [18, 19]. Additional benefits of regular postpartum physical activity include boosting energy, promoting better sleep, preventing or reducing the symptoms of postpartum depression, restrengthening the abdominal wall muscles to reduce the incidence of diastasis recti abdominus, and reducing lumbopelvic pain [20,21,22].

Determining the safest time to return to the suggested level of weekly physical activity postnatally depends on several factors, including mode of delivery, degree of perineal trauma, incontinence, severity of anemia, presence of medical or surgical complications, and personal preferences. For patients with uncomplicated deliveries, physical activity can be resumed very shortly after delivery with light-intensity, progressing to moderate over time. While there is limited data evaluating the effect of an early return to activity on pelvic floor function, data from a randomized controlled trial of patients undergoing reconstructive pelvic surgery demonstrated fewer urinary and prolapse symptoms in those allowed to return to activity at their own pace versus those with restricted activity for 3 months postoperatively [23]. Kegel pelvic floor strengthening exercises can be initiated 2 to 14 days after delivery in patients without obstetric anal sphincter injury or episiotomy; these exercises can be deferred if the exercise incites pain. Core strengthening exercises can be initiated at any time following vaginal birth; a list of 5 easy-to-perform abdominal exercises are available on the American College of Obstetricians and Gynecologists (ACOG) website [24].

Following cesarean birth, early ambulation (as soon as 4 hours after skin closure) is recommended as part of an Enhanced Recovery After Cesarean (ERAC) protocol [25]. Early ambulation reduces the time to return of bowel function, risk of thrombosis, and postpartum length of stay [25]. Use of stairs at home with assistance while moving at a deliberate pace is allowable. Regarding lifting weights, data are lacking to guide safe upper weight limits. As only 50–60% of the abdominal fascia strength is restored at 6 weeks postpartum, a cautious approach is sensible. ACOG offers a general recommendation to temporarily restrict the amount of weight lifted to no more than that of the newborn [26].

Lactation

The American Academy of Pediatrics recommends exclusive breastfeeding for the first 6 months followed by continued breastfeeding with complementary foods for at least 2 years [27]. Lactation is an energy intensive state which theoretically could elicit a net-negative balance contributing to postpartum weight loss. However, studies vary on whether breastfeeding without additional caloric restriction or exercise is enough to combat postpartum weight retention [28].

The Dietary Guidelines for Americans (2020–2025) recommends an additional 330 cal in the first 6 months postpartum and 400 cal between 6 and 12 months postpartum compared to prepregnancy needs for lactating patients [29]. The Calculator for Health Care Professionals provides guidance for daily nutrient and calorie thresholds to meet nutritional requirements based on age, body mass index, activity level, and pregnancy or lactation status [30]. In patients that have established a consistent breastmilk supply and are motivated to lose weight, providers can prescribe a diet that is 500 fewer calories per day (the energy output of breastfeeding), maintaining a minimum of at least 1800 cal per day. This should elicit a moderate weight loss of 1 pound per week, which over 4 months, can help a patient return to their prepregnancy weight without negatively impacting infant growth [31].

During lactation, adhering to a balanced diet including all classes of macronutrients is crucial for maintaining the composition and quantity of breast milk produced. Several of the fad diets popularized in the US media (e.g., very low carbohydrate, paleolithic, very low fat) can lead to nutritional deficiencies in lactating women and should be avoided [32]. Meal plans should emphasize nutrient-dense whole foods such as fruits, vegetables, legumes, whole grains, and healthy fats [32]. Patients opting for a vegan diet should have assessment and repletion of folate, vitamin B12, iron, zinc, choline, iodine, and EPA/DHA [31].

Pharmacotherapy

Specifics on drug selection, dosing, and monitoring of weight loss medications are beyond the scope of this article, but it is important to acknowledge that the market for medical weight loss has risen exponentially in the past 2 years. Clinicians wrote more than 9 million prescriptions for Ozempic®, Wegovy®, and similar medications between October and December of 2022 [33].

There are numerous medications with US Food and Drug Administration approval for the treatment of overweight and obesity. The preferred medications for weight loss are glucagon-like peptide 1 (GLP-1) receptor agonists with or without dual agonist action for gastric inhibitory polypeptide (GIP). GLP-1 receptor agonists are anorectics which act on the hypothalamus and have several effects: reduced appetite, increased satiety by inhibiting gastric emptying, inhibited glucagon release, decreased insulin resistance, and stimulated glucose-dependent insulin secretion. Other classes of weight loss drugs include amphetamine derivatives, naltrexone-bupropion, and pancreatic lipase inhibitors. For best effect, weight loss medications should be used in conjunction with diet, lifestyle modification, and physical activity. Most patients will experience a rebound weight gain upon medication discontinuation, and thus continued lifelong use is recommended [34].

Postpartum patients may be candidates for medical treatment of weight loss if they have a BMI of at least 30 kg/m2 (or BMI 27–29.9 kg/m2 plus metabolic disease) and have not achieved a 5% weight loss despite 6 months of a comprehensive lifestyle intervention. One randomized controlled trial found that for patients who experienced gestational diabetes, postpartum treatment with an 84-week course of liraglutide (a GLP-1 receptor agonist) plus metformin was more efficacious than metformin monotherapy in reducing body weight, central adiposity, and insulin resistance (notably, this trial was limited by a high attrition rate in both arms) [35].

Intentional weight loss and the use of the weight loss medication is not recommended in pregnancy due to adverse effects and safety concerns [10]. Animal studies have demonstrated teratogenic effects with GLP-1 agonists, including reduced embryonic survival, delayed ossification, skeletal variations, and poor fetal growth [36]. Human data of periconception GLP-1 use has shown a 6% incidence of major congenital malformations in offspring [37]. Amphetamine derivatives are also not recommended in pregnancy and are associated with an increased risk for orofacial clefts, fetal growth restriction, and stillbirth. Lastly, medications that reduce intestinal fat absorption may lead to fat-soluble vitamin deficiencies and their associated risks for pregnancy. Timing for discontinuation of weight loss drugs prior to conception depends on the half-life; for GLP-1 agonists, they should be discontinued 2 months prior to conception [38].

There is limited data regarding medical weight loss and lactation. It is not known if GLP-1 agonists, GIP agonists, pancreatic lipase inhibitors (e.g., Orlistat), or amphetamine derivatives (e.g., Phentermine) are present in breast milk. Naltrexone-bupropion and its metabolites are excreted in breast milk; while naltrexone has not been shown to have any negative infant effects, there are case reports of possible seizures in partially-breastfed infants exposed to bupropion. Topiramate is often combined with Phentermine and is present in breast milk; diarrhea, somnolence, irritability, hypertension, sleep changes, tremor, vomiting, and weight loss have been reported in exposed infants. Given the lack of available safety data, weight-management medications are not recommended during breastfeeding [39].

Surgery

Metabolic and bariatric surgery (MBS) is arguably the most effective and definitive management for obesity and therefore has a potential role in postpartum weight loss. Its use has increased steadily over the last 3 decades, with sleeve gastrectomy accounting for 70% of bariatric surgeries performed in 2015 [40]. The complication rate of MBS is as low as 1.4%, making it a safe option for many patients [41].

The American Society for Metabolic and Bariatric Surgery and the International Federation for the Surgery of Obesity and Metabolic Disorders published new guidelines for the indications for MBS in 2022 [42]. MBS is recommended in patients with a BMI of at least 35 kg/m2, regardless of the presence or absence of comorbidities, because current nonsurgical options are ineffective in generating sustained weight loss significant enough for general health improvement. MBS is also recommended for patients with class I obesity (BMI 30–34.9 kg/m2) and metabolic disease with an unsuccessful trial of pharmacotherapy. For patients of Asian ethnicity, the rates of diabetes and cardiovascular disease are higher at a lower BMI than for non-Asian populations; therefore, different thresholds for diagnosing obesity are suggested for patients of Asian ethnicity, such that MBS should be offered at a BMI of 27.5 kg/m2.

There are three types of MBS procedures: restrictive, malabsorptive, and combined malabsorptive-restrictive. Restrictive procedures cause weight loss by limiting the reservoir capacity of the stomach and thereby caloric intake; these include sleeve gastrectomy and adjustable gastric band. Malabsorptive procedures reduce nutrient absorption by shortening the functional small intestine; these include jejunoileal bypass and biliopancreatic diversion with or without duodenal switch. Roux-en-Y gastric bypass is a combined procedure. MBS procedures lead to a 30–40% total body weight loss at 2 years postoperatively.

Due to the rapid and massive weight loss following MBS, it is suggested that patients wait 1–2 years after the procedure before conceiving to allow for maximum weight loss without exposing the fetus to the weight loss environment [43]. Patients should be advised that fertility rates increase after MBS due to improvements in anovulatory conditions, and oral contraceptive pills (progestin-only and combined) are less efficacious in a patient with malabsorptive MBS [44, 45]. Many obstetric outcomes are improved for patients who conceive post-MBS compared to patients with obesity without MBS. The risk of preeclampsia is reduced by approximately 50%, gestational diabetes by 40%, chorioamnionitis by 55%, cesarean delivery by 35%, large for gestational age infant by about 80%, and neonatal intensive care unit admission by 30% [46]. There is, however, an increased risk for small for gestational age infant, so ultrasounds for fetal growth can be considered [46, 47]. Screening for and correcting micronutrient deficiencies is paramount to supporting a healthy pregnancy in a patient with MBS.

Conclusion

Clinicians should provide patients with education about the risks of postpartum weight retention and supply them with the resources to succeed in weight loss efforts. Behavioral interventions should be multifaceted and include both nutrition and physical activity guidance. Free digital content for at-home bodyweight exercises is much more prevalent, so physical activity can reasonably occur within the confines of one’s home. Though nutrition is essential to weight loss, access to nutritious and affordable foods is not universal and thus public funding to ameliorate food desserts in impoverished zip codes has the potential to improve access.

Pharmacotherapy is a reasonable adjunct to lifestyle modification in patients with obesity. As most current weight loss medications are not considered safe to use in pregnancy, patients should be counseled on reliable contraceptive methods or on drug discontinuation prior to conception. Lactation safety data is lacking, so future research is needed to ascertain drug excretion into breastmilk and effects on breastfed infants.

Bariatric surgery remains an option for patients with obesity and coexistent metabolic sequelae who have failed pharmacotherapy or in patients with class II-III obesity (BMI ≥ 35). Pregnancy should be delayed 1–2 years following bariatric surgery so as not to expose the fetus to the peak weight loss environment.

Further research is needed to optimize postpartum weight loss interventions. This includes determining the ideal timing, frequency, and intensity of lifestyle changes for long-term weight management, as well as investigating how evolving handheld technologies can be best integrated for patient support.