Breastfeeding and obesity: a meta-analysis

doi:10.4236/ojpm.2011.13013

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Vol.1, No.3, 88-93 (2011)

doi:10.4236/ojpm.2011.13013

Open Journal of Preventive Medicine

Breastfeeding and obesity: a meta-analysis

Jeanne M. Stolzer

University of Nebraska-Kearney, Kearney, USA; stolzerjm@unk.edu

Received 3 September 2011; revised 15 October 2011; accepted 24 October 2011.

ABSTRACT

Over the last decade, obesit y rates have reached

epidemic proportions in the United States of A-

merica. Comorbidities associated with overweight

and obesity include, but are not limited to, hy-

pertension, type 2 diabetes, cardiovascular di-

sease, and elevated cholesterol levels. As a di-

rect result of obesity, data indicates that these

diseases are now being detected in an unpre-

cedented number of American children, ado-

lescents, and adults. Although the major cause

of the obesity epidemic in America has thus far

been attributed to excessive caloric intake and

lack of physical activity, this paper will explore

the pivotal role that breastfeeding plays in the

prevention of overweight and obesity through-

out the life course. Epide miological data demo n-

strates that breastfeeding significantly reduces

the incidence of overweight and obesity and

that exclusive and long term breastfeeding has

been strongly correlated with a reduction in LDL

cholesterol, blood pressure related disorders,

type 2 diabetes, and cardiovascular dysfunction.

While it is certain that diet and exercise are in-

tegral factors associated with overweight and

obesity, the time has come for a collective re-

cognition of the protective effects associated

with breastfeeding if we are serious in our en-

deavor to eradicate the overweight and obesity

epidemic in America.

Keywords: Obesity; Breastfeeding and Obesity;

Breastfeeding; Lactation and Obesity

1. INTRODUCTION

Over the last 40 - 50 years, much attention has been

given to the role of diet and exercise with regard to the

prevention of obesity. It is certainly a fact that the

American diet has been altered dramatically in a rela-

tively short time. Portion sizes in food outlets have more

than doubled over the last two decades, and Americans

have significantly increased their consumption of fatty

fast foods [1]. In addition, trans-fats are now a common

ingredient in a variety of foods and natural home pre-

pared meals are becoming increasingly rare.

In addition, Americans are now more sedentary than

at any time in recorded history. Walking, which has been

an integral feature of hominid existence throughout evo-

lutionary time, has now been replaced by riding in cars,

elevators, and other automated means of transportation

[2]. Children no longer spend their days engaged in rig-

orous physical outdoor activity, but instead rely on high-

tech gadgetry to occupy their time [3]. Physical educa-

tion classes have been systematically reduced or elimi-

nated, and recess is no longer considered a necessary

component of the American public school curriculum

[3,4].

According to the American Academy of Pediatrics [5],

preventio n of obesity in children must be the first line of

defense. The American Academy of Pediatrics [5] re-

leased a policy statement that recommended that pedia-

tricians should become adept at recognizing children at

risk of overweight and obesity. In addition, pediatricians

should calculate and plot Body Mass Index (BMI) at

every visit, use changes in BMI to identify excessive

weight gain, and monitor for comorbidities associated

with obesity. The American Academy of Pediatrics [5]

also states that pediatricians should encourage, support,

and protect breastfeeding in order to significantly de-

crease overweight an d obesity in child pop ulations [2,5].

It is interesting to note that at the same time the

American Academy of Pediatrics (AAP) [5] is promot-

ing the multifarious benefits of breastfeeding, they are

also aligned economically with the formula industry.

The AAP [5] routinely advertises formula in the presti-

geious medical journal “Pediatrics,” was granted three

million dollars by the manufacturers of formula to build

the AAP headquarters in Illinois, and is funded in part

by block grants provided by the formula industry [6,7].

If the AAP [5] is sincere in its efforts to promote

breastfeeding as a means to combat overweight and obe-

sity, perhaps the time has come to sever its economic

ties with the formula industry. Margolis [8] forcefully

J. M. Stolzer / Open Journal of Preventive Medicine 1 (2011) 88-93

reiterates this position by stating “The acceptance of

gifts in virtually any form violates the fundamental du-

ties of the physician of nonmaleficence, fidelity, justice,

and self improvement; the medical community must

articulate this position clearly, and it should act accord-

ingly” (p. 51).

Clearly, the prevention of this epidemic should be our

focus as data confirms that a high body mass index (BMI)

in childhood is a strong predictor of overweight and

obesity during adolescence and adulthood [9]. Increasing

breastfeeding initiation and duration will, according to

published data, significantly decrease overweight and

obesity, thus decreasing morbidity and mortality rates

across the life span [10,11]. Obesity related diseases

such as cardiovascular disease, high blood pressure, ele-

vated cholesterol, and type 2 diabetes are manifested in

both children and adults, therefore, early intervention is

critical [5,12].

2. BENEFITS OF BREASTFEEDING

In keeping with the guidelines set forth by the Sur-

geon General of the United States [13] and the World

Health Organization [11], infants should be exclusively

breastfed for the first six months of life, with continued

breastfeeding for two years or longer. According to

decades of empirical, epidemiological data, breastfeed-

ing has been associated with significant decreases in

morbidity and mortality rates across the life course [13].

Breastfeeding has also been correlated with a reduction

of infectious and noninfectious diseases, diarrhea, respi-

ratory illness, ear infection, type 1 and 2 diabetes, celiac

disease, inflammatory bowel disease, childhood cancer,

allergies, asthma, overweight, and obesity [14,15].

Numerous scientific studies have confirmed that chil-

dren who are breastfed exclusively and long term are

less likely to develop botulism, bacterial meningitis,

urinary tract infection, liver disease, and sudden infant

death syndrome (SIDS) [14,16]. Furthermore, research-

ers have found that breastfeeding significantly decreases

hospital admission rates and prescription drug use in

pediatric populations [14,1 7] .

3. BREASTFEEDING AND OBESITY:

EPIDEMIOLOGICAL EVIDENCE

For over forty years, epidemiological studies have

demonstrated that breastfeeding significantly reduces

both overweight and obesity in child, adolescent, and

adult populations [18-20]. In addition , empirical data h as

confirmed that nutritional intake in infancy is highly

correlated with later predisposition to diseases such as

obesity, high blood pressure, heart disease, and type 2

diabetes [21,22].

It has been established that cow milk contains signify-

cantly higher levels of protein and fat than human milk.

The high fat and protein levels found in bovine based

formula lead to an increased secretion of IGF-1 (insulin

growth factor type 1 and in turn stimulates the over-

production of adipocytes which has been associated with

overweight and obesity in human populations [23]. Hu-

man milk is compositionally distinct from all other

mammalian milk as milk from a particular mammal is

species specific (i.e., ensures the optimal development of

that particular mammal). Cow milk contains three times

the amount of protein that human milk contains, as the

survival of most mammals is dependent on the rapid

acceleration of physical growth. However, humans are

distinct from most mammals in this respect [24].

Human milk is quantitatively different than formula

regardless if it is soy or bovine based. Numerous bioac-

tive factors are exclusive to human milk, including spe-

cific human growth hormones and growth factors which

impact differentiation, growth, and fu nctional maturation

of the human organism [25,26].

The concept that early nutritional intake influences

adult onset overweight and obesity was first developed

by McCance [20] in the 1960’s. Kramer [18] continued

on with McCance’s seminal work and demonstrated with

empirical case-controlled studies that formula feeding in

infancy was significantly linked to obesity in adoles-

cence and adulthood. Animal studies have also been va-

luable as they show the particular mechanisms that link

early nutrition with accelerated growth, appetite regula-

tion, and the underlying hormonal factors which have

been correlated with overweight and obesity in human

subjects [27].

It has been suggested that one of the reasons that for-

mula-fed infants are more likely to develop overweight

and obesity later in life is that there are predetermined

amounts of formula that a baby is supposed to drink.

Physicians and/or the manufacturers of formula recom-

mend specific dosages which often times leads to over-

eating and the inability to determine satiety [25]. Con-

versely, a breastfed baby has no predetermined amount

they are supposed to drink at each feeding. Across mam-

malian species, the exclusively breastfed baby suckles

until satisfied. There is no overfeeding and the infant

learns appetite regulation beginning immediately after

birth [28].

Longitudinal data demonstrates that breastfeed ing acts

as a buffer against overweight and obesity even when

controlling for confounding variables such as socioeco-

nomic status, education of parents, race, number of sib-

lings, and maternal BMI [29,30]. Gillman and Collea-

gues [31] found that the effects of breastfeeding are

dose-response specific, as their data indicates that the

J. M. Stolzer / Open Journal of Preventive Medicine 1 (2011) 88-93

longer a child is breastfed, the less likely the child is to

become overweight or obese in later life.

Armstrong & Reilly [29] assessed 32, 2000 children

and found the most statistically powerful results were

detected in exclusively breastfed populations. Those

subjects who were formula fed in infancy were signify-

cantly more likely to develop overweight and obesity

during later childhood. These results are critical as they

demonstrate the protective effects of exclusive breast-

feeding as opposed to formula feeding or breastfeeding

using formula supplem ent at ion.

Bergman, et al. [32] conducted a longitudinal birth

cohort study that tested whether exclusive breastfeeding

was correlated with BMI at six years of age. They

looked at newborns with almost identical BMI’s, and

revisited these infants at three months of age, and at four,

five, and six years of age. At every interval, the formula

fed children had significantly higher BMI’s and thicker

skin folds than the breastfed cohort. At the ages of four

through six, the prevalence of obesity tripled in the for-

mula fed population.

Other researchers have found that breastfeeding sig-

nificantly decreases ov erweight and ob esity in childhood

regardless of maternal diabetes status, or weight status

[33]. Gillman and Colleagues [31] work demonstrates

that overweight during adolescence predicts short and

long term morbidity as well as obesity in adulthood.

According to Gillman, et al, formula feeding in infancy

is a significant predictor of adult overweight and obesity

even when controlling for variables such as gender, en-

ergy intake, time watching TV, physical activity, mo-

ther’s BMI, and socioeconomic status.

Decades of systematic reviews of epidemiological

studies (cohort, case-control, cross-sectional, and longi-

tudinal studies) have compared breastfed and formula

infants. These studies have adjusted for a multitude of

confounding variables such as gender, race, age, mater-

nal status, parental education, birthweight, and geo-

graphical location. All of these studies have concluded

that breastfeeding plays a significant role in reducing

overweight and obesity in child, adolescent, and adult

populations [18,32,33]. Additional research have clearly

demonstrated the dose-response specifity of breastfeed-

ing as data confirms that the longer a child is breastfed,

the stronger the protective effect of breastfeeding against

overweight and obesity throughout life [31,34].

4. COMORBIDITIES ASSOCIATED WITH

OVERWEIGHT AND OBESITY

Numerous studies have concluded that breastfeeding

not only decreases the prevalence of overweight and

obesity, but is also inversely related to the development

of type 2 diabetes, elevated blood pressure and choles-

terol, and cardiovascular disease.

5. TYPE 2 DIABETES

The rates of type 2 diabetes are higher now then at

any other time in recorded American history [2]. Over-

weight and obesity are thought to precipitate type 2 dia-

betes by interfering with insulin signaling as excess fat

in the muscle cells leads to physio logical atrophy result-

ing in hyperglycemia and chronic glucose intolerance

[35]. Exclusive breastfeeding has been found to protect

individuals from type 2 diabetes by encouraging optimal

lipoprotein metabolism and gastrointestinal adaptation

[2].

Exclusive breastfeeding has also been correlated with

lower fasting insulin concentrations and lowered pre-

prandial blood glucose lev els in adults [36]. Ravelli [37]

studied a co hort of sub jects that w ere born between 1943

and 1947 in Amsterdam. Ravelli’s data revealed that

those adults who were exclusively breastfed were sig-

nificantly less likely to be diagnosed with type 2 diabe-

tes when compared to those subjects who were partially

or exclusively formula fed.

Although investigations are still ongoing, there exists

substantial evidence to support the supposition that

breastfeeding acts as a buffer with regard to the develo-

pment of type 2 diabetes in child, adolescent, and adult

populations [5,9 ,13,15,36].

6. ELEVATED BLOOD PRESSURE AND

CHOLESTEROL

According to the World Health Organization [15],

elevated blood pressure in adolescence and adulthood

has been correlated with formula feeding in infancy.

Martin and Colleagues [38] conducted a systematic re-

view which included over 17,000 adults and found that

systolic blood pressure was significantly lower in sub-

jects who were exclusively breastfed during infancy.

Martin, et al. [38] acknowledged that the particular me-

chanisms underlying these findings are not fully under-

stood at this time, and that more research is needed in

this area.

Plagemann & Harder [39] found that breastfeeding

positively impacts bo th HDL and LDL cho lesterol levels

and significantly reduces blood pressure in adolescents

and adults. Waterland & Garza [22] hypothesized that

the metabolic imprinting that occurs with formula feed-

ing actually alters vascularization and cell structure

causing changes in the production of enzymes, hormones,

and transmembrane transporters. Waterland & Garza [22]

suggest that this metabolic alteration significantly in-

creases the risks of later cardiovascular disease.

Although nu merous studies have indicated that exclu-

J. M. Stolzer / Open Journal of Preventive Medicine 1 (2011) 88-93

sive breastfeeding has been associated with a protective

effect against elevated blood pressure and elevated cho-

lesterol levels later in life [40], researchers have ac-

knowledged that the mechanisms which regulate lipo-

protein concentrations and blood pressure functioning

need further investigation. What is certain at this point is

that breastfeeding is statistically related to the prevention

of metabolic atrophy in human populations [15,25,40].

7. CARDIOVASCULAR ATROPHY

A number of studies have indicated that elevated BMI

is correlated with cardiovascular disease [5,9,15,35], and

that childhood overweight and obesity are significant

predictors of la t e r cardi o vascular, dysfunct i o n [2 ,4 1, 2].

Published data indicates that formula feeding increase s

the risks of later cardiovascular disease. Rich-Edwards,

et al., [42] examined over 87,000 individuals observing

differences in feeding methods and later cardiovascular

malfunction. Participants were born between 1921 and

1946 and reported in 1992 if they were breastfed or for-

mula fed, and for how long they were breastfed. During

eight years of investigation, these researchers found that

breastfed populations had significantly lower rates of

cardiovascular disease and stroke. The most significant

protective effects of breastfeeding were observed in

those participants who were breastfed for nine months or

longer.

Owen, Whincup, Odoki, Gilg, and Cook [43] cross

sectional study suggests that breastfeeding plays a major

role in the prevention of cardiovascular disease. Ac-

cording to this study, breastfeeding is associated with

lower LDL cholesterol and blood pressure, and has long

term benefits for cardiovascular functioning.

The widely known Muscatine Study demonstrated that

cardiovascular risk in adulthood is related to childhood

LDL cholesterol levels and childhoo d BMI [41]. In addi-

tion, postmortem studies have indicated that with regard

to atherosclerosis, the extent and severity of cardiovas-

cular disease is highly correlated with elevated BMI and

lipoprotein levels [2].

Researchers have postulated that infant nutrition is a

reliable predictor of later cardiovascular functioning.

Tracy, Newman, Wattigney, and Berenson [44] con-

cluded that atrophy of the arterial wall most likely oc-

curs during childhood as data indicates that formula

feeding in infancy is a more powerful predictor of car-

diovascular disease then is adult risk factors.

8. CONCLUSIONS

It has been well established that breastfeeding signify-

cantly decreases overweight and obesity and those co-

morbidities associated with these conditions [5,15]. How-

ever, any discussion regarding increasing breastfeeding

rates in America must take into account the multifarious

variables associated with this issue. In order to increase

breastfeeding rates across diverse populations, research-

ers must acknowledge the complexities associated with

breastfeeding, which include, but are not limited to 1)

The lack of breastfeeding role models in the family, the

community, and the mass media [28]; 2) federal policies

which impede both the initiation and duration of breast-

feeding [6,17]; 3) culture ideologies which dictate that a

woman’s worth is based on her economic earning power

[28]; 4) the lack of physician breastfeeding education

[13,16] and 5) The mass sexualization of the female

breast [7,16].

The Surgeon General [13] has stated that increasing

breastfeeding rates is essential, and has urged research-

ers to improve the public’s understanding of the com-

pendious benefits associated with breastfeeding [13]. At

the present ti me, the United States of America has one of

the lowest breastfeeding rates in the world, and contin-

ues to rank significantly higher than other industrialized

nations in terms of morbidity and mortality rates [15]. If

we are to see a reduction in overweight and obesity,

American’s can no longer afford to ignore the protective

effects of breastfeeding which have been well docu-

mented in the medical literature.

In light of the overwhelming body of scientific evi-

dence that documents the risks associated with formula

feeding, the medical profession, parents, researchers,

educators, and concerned others must strengthen their

advocacy of breastfeeding. We can no longer claim that

breastfeeding and formula feeding are equal methods of

nutrition, or that health outcomes are the same for

breastfed and formula fed populations.

Data confirms that breastfeeding in infancy is associ-

ated with a reduced risk of overweight and obesity, type

2 diabetes, elevated blood pressure and cholesterol, and

cardiovascular disease [5,11,12,36]. While the decrease

in caloric intake and an increase in physical activity are

the primary environmental protections against over-

weight and obesity, preventative strategies such as in-

creasing breastfeeding initiation and duration rates are

essential if we are to be successful in reversing the

overweight and obesity epidemic in future generations

[5]. Accordingly, we must address this obesity crisis by

making breastfeeding a public health priority, and by

uniting forces across disciplines to support a strong and

effective public health campaign to increase breastfeed-

ing rates exponentially [10,11].

9. FUTURE DIRECTIONS

Extensive epidemiological data demonstrates that ex-

clusive breastfeeding has long term benefits including

J. M. Stolzer / Open Journal of Preventive Medicine 1 (2011) 88-93

the reduction of obesity and overweight, type 2 diabetes,

blood pressure, LDL cholesterol levels, and cardiovas-

cular disease [5,10,15,37]. The inverse relationship be-

tween breastfeeding and th e above stated risk factors can

no longer be ignored. According to decades of published

empirical data, breastfeeding significantly impacts health

outcomes not only in childhood, but throughout the

life-span [14,16,11].

In order to increase breastfeeding rates exponentially,

experts have suggested the following:

 Requiring that the formula industry inform the Ame-

rican consumer of the risks associated with their pro-

duct [7,16].

 Incorporating breastfeeding role models in the famil-

ial sphere, the community, and the mass media [7].

 Regulating the advertising of formula, particularly in

medical journals and parenting magazines [7].

 Demanding that the economic alliance between the

medical community and the formula industry be sev-

ered, including a halt to the formula industry’s fund-

ing of medical research, as well as its practice of giv-

ing free samples to new mothers via hospitals or

physician offices [28].

 Reassessing America’s cultural view of the female

breast [16,28].

 Providing mandatory continuing breastfeeding edu-

cation for practicing physici ans [16,17].

 Formally questioning the ethics of medical journals

that carry advertisements for formula (a product that

is known to increase morbidity and mortality rates)

[28].

 Demanding that the public be informed via public

service announcements of the protective effects of

breastfeeding.

 Requiring physicians to inform their patients that

breastfeeding significantly decreases morbidity and

mortality rates (including overweight and obesity).

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