Early Weaning & Introduction of Solids Increases Obesity Risk

by Mary Elizabeth Dallas
February 27, 2011

Formula-fed infants introduced to solid foods before they are 4 months old are at greater risk for becoming obese by the time they are 3 years old, according to a new study from Harvard published in the February 2011 issue of Pediatrics.

Childhood obesity is a global epidemic and a critical public health challenge. The problem is not limited to school-aged children and adolescents. Statistics show obesity is widespread even among infants and toddlers. In fact, the prevalence of overweight American infants and toddlers has surged by 60 percent in the past three decades.

The Centers for Disease Control and Prevention (CDC) reports an estimated 17 percent of children ages 2–19 are obese. Among preschool-age children 2–5, the prevalence of obesity doubled to 10 percent between 1976 and 2008.

Research
Researchers from Children’s Hospital Boston, Harvard Medical School/Harvard Pilgrim Health Care Institute, and the Harvard School of Public Health followed 847 infants for three years to examine the association between the introduction of solid foods and obesity. In the first four months of life, 67 percent of the infants were breastfed and 32 percent were formula-fed. All babies were introduced to solid foods between the ages of 4–6 months.

Results
The researchers concluded that infants who never breastfed or those who stopped breastfeeding before the age of 4 months, and were given solid food before the age of 4 months, were six times as likely to be obese at 3 years of age than their counterparts who were introduced to solid foods after 4 months of age.

Among exclusively breastfed babies in the study, the introduction of solid food had no effect on whether or not they were obese at 3 years of age. Babies who were formula-fed, or who stopped breastfeeding before they were 4 months old however, had a one in four chance of being obese at age 3, if they started eating solid foods before they were 4 months old. If parents introduced solid foods between 4 and 5 months, the infant’s chances of being obese were 1 in 20.

So how can the link between obesity and the introduction of solid foods among formula-fed infants be explained? The study argues that formula-fed infants may increase their energy intake when solids are introduced. In short, they may eat more.

These findings were supported by another study conducted at the University of California, Davis, which revealed that solid foods introduced before the age of 6 months displaced milk intake among breastfed but not formula-fed infants. Another 2006 study from the UK found that solid food introduction before the age of 4 months was related to higher energy intake in formula-fed but not breastfed infants.

Larger infant size, or the perceived need for more than breast milk or formula for adequate growth, as well as the perception of hunger in an infant also seem to influence parents’ decisions to introduce solid foods early.

A separate Chapel Hill study found that infants perceived to be fussy were nearly twice as likely to be fed solid food before 4 months of age. The study collected information from a group of 217 low-income, black, first-time mothers. Researchers found that about 70 percent of the infants were fed some breast milk during the first month of life. About 20 percent of the infants were breastfed exclusively, but by 3 months of age, 75 percent of infants were introduced to either solids or juice. The study authors suggest that breastfeeding may not only promote self-regulation of an infant’s energy intake, but may also help mothers learn to recognize their infant’s hunger and satiety cues.

Recommendations
The World Health Organization recommends exclusive breastfeeding for six months. Guidelines from the American Academy of Pediatrics (AAP) recommend that mothers breastfeed exclusively (no formula, water, juice, or solid foods) for at least four months, but preferably six months.  The AAP also states that solid foods should be introduced when infants are about 6 months of age. Despite these guidelines, roughly 25 percent of infants in the United States are never breastfed, and about 50 percent of infants are breastfed for less than four months, the CDC reports.

The first few months after birth may be a critical window in the fight against childhood obesity, the Harvard study contends, because parental feeding practices during early infancy, particularly the timing of solid food introduction, can be controlled.

Solid foods can be introduced as early as 4 months, but ultimately, babies need a digestive system that is mature enough to handle solid foods along with the ability to move solids to the back of their mouth and swallow. So the best advice for parents is to watch your baby, not the calendar.

You will know your baby is ready for solid foods if she:

• sits upright with little or no support;
• holds her head upright and steady;
• moves food to the back of her mouth and swallows, showing no signs of the “extrusion reflex” (a newborn reflex that causes her to push food out of her mouth with her tongue);
• shows an interest in solid foods by watching what you eat or by grabbing food from your plate (if your baby doesn’t react willingly to a spoon touching her lips, it is likely she is trying to communicate that she is not ready).

The newest study adds even more evidence that mothers who initiate breastfeeding and continue breastfeeding beyond three to five months are more likely to delay the introduction of solid foods to at least 4 months of age. It is this winning combination of continued breastfeeding and later introduction of solids (6 months) that may significantly reduce the risk of childhood obesity.