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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Weight Gain & Energy Needs

How Much "Eating for Two" Really Means

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

0 human trials, about 24 studies, IOM/NASEM guidelines + cohort data. The written rationale for this grade is still being prepared.

FDA
Guideline-based (IOM/NASEM weight-gain ranges; ACOG)
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

Weight and eating in pregnancy are sensitive, and this entry describes population patterns rather than a plan for any individual. Both directions of gain carry documented associations: excessive gestational weight gain is linked in large cohort analyses to gestational diabetes, hypertensive disorders of pregnancy, cesarean delivery, and large-for-gestational-age or macrosomic babies, while inadequate gain is linked to small-for-gestational-age babies, low birth weight, and preterm birth. Because both extremes matter, the goal is a range appropriate to a person's starting weight rather than the lowest possible number, and deliberate calorie restriction or weight-loss dieting is not advised during pregnancy. Anyone weighing questions about their own gain, energy needs, or eating, including those with a history of disordered eating, should work through them with an obstetric provider or a registered dietitian who can individualize the guidance safely. This entry does not offer calorie targets, gain targets, or a diet.

The phrase "eating for two" badly overstates the real need. Energy requirements rise only modestly in pregnancy: no routine increase in the first trimester, about 340 extra calories a day in the second and about 452 in the third, nowhere near a second adult's worth. How much total weight gain is appropriate depends on where someone started, and the widely used 2009 Institute of Medicine ranges run from about 28 to 40 pounds for a person who began underweight down to 11 to 20 pounds for one who began with obesity. Most pregnant people in the United States gain outside their range, more often above it than below. Both directions carry documented risk, which is why the aim is a range suited to the individual rather than a single number, worked out with a provider.

"Eating for two" is one of the most persistent prenatal myths; the actual extra energy need is modest and weight-gain targets depend on starting weight.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Setting realistic energy expectations across the three trimesters
  • Understanding that appropriate weight gain is a range keyed to pre-pregnancy weight, not a universal number
  • Recognizing that both excessive and inadequate gain carry documented risks
  • Framing lactation's higher energy demand relative to pregnancy
  • Countering the "eating for two" framing without tipping into restriction

What people get wrong

  • Often saidYou need to eat for two during pregnancy.

    ActuallyThe extra energy need is modest and it climbs gradually: no routine addition in the first trimester, about 340 calories a day in the second and about 452 in the third, per the IOM Estimated Energy Requirements, far from doubling. Reading "eating for two" literally is one route to excessive gain, which the Goldstein 2017 meta-analysis links to larger babies and macrosomia.

  • Often saidThere is one weight-gain number everyone should aim for.

    ActuallyThe 2009 IOM ranges span roughly 11 to 40 pounds across weight categories, from about 28-40 pounds for someone who began underweight to 11-20 pounds for someone who began with obesity. The appropriate target is individual, and the right answer for one person can sit well outside another's range.

  • Often saidGaining a little less than recommended is the safe side to err on.

    ActuallyInadequate gain carries its own documented risks. In the Goldstein pooled cohort, gain below the recommendations was associated with small-for-gestational-age babies (OR 1.53) and preterm birth (OR 1.70). This is why deliberate weight-loss dieting is not advised in pregnancy and why targets are set as ranges rather than ceilings.

  • Often saidOnce the baby arrives the extra energy demand drops off.

    ActuallyExclusive breastfeeding is more energy-costly than pregnancy itself. Reference bodies estimate roughly 500 extra calories a day during lactation (the National Academies place the first-six-months net cost near 500 kcal before accounting for fat stores laid down in pregnancy), more than the second or third trimester asks.

Who profits, and who pushes back

  • Institute of Medicine / NASEM

    championsGestational weight-gain guidelines (2009)

    Recommended total weight gain is 25-35 lb for normal-weight women, with different ranges by pre-pregnancy BMI; gaining within these ranges supports better outcomes.

  • ACOG

    endorsesObstetric guidance

    Energy needs rise modestly, about 340 kcal/day in the second trimester and 450 in the third; weight gain should be individualized and excessive gain avoided.

  • Maternal-nutrition dietitians

    endorsesLactation energy needs

    Breastfeeding requires roughly an extra 500 calories per day, more than pregnancy itself, which is often underappreciated.

  • Anti-restriction caution

    caveatsEating-pattern safeguard

    Weight guidance must not become restrictive dieting, which is unsafe in pregnancy; the goal is appropriate gain, not deprivation.

Where the research comes from

Most of the published research on this comes from one place. 68% of it is from Outside recommended. Findings that no unrelated group has reproduced are weaker than the study count makes them look.

Share of published research by country of origin.
PlaceShare of published research
Outside recommended68%
Within recommended gain32%

Research published from: Global (ranges vary).

How we got here

For most of the twentieth century the instinct in obstetrics ran toward restriction. From the late 1800s many clinicians advised dieting to hold gain under about 20 pounds, on the belief that heavy gain caused toxemia, and mid-century advice sometimes pushed limits as low as 10 to 14 pounds when eclampsia was often fatal. The turn came with attention to infant mortality: in 1970 the US Committee on Maternal Nutrition, noting the link between maternal gain and birth weight, raised the target to 20 to 25 pounds for all women. The Institute of Medicine's 1990 report replaced a single number with ranges tied to pre-pregnancy weight, and its 2009 revision aligned those categories with World Health Organization body-mass cutoffs and, for the first time, set a specific range for pregnant people with obesity. Through all of it the "eating for two" folklore outlasted the modest measured energy need, and modern guidance has spent decades correcting it while stressing that too little gain carries its own harms.

  1. Late 1800sObstetricians commonly advise dieting to keep pregnancy gain under about 20 pounds, blaming heavy gain for toxemia
  2. 1950sSome guidance restricts gain to 10-14 pounds during an era when eclampsia is frequently fatal
  3. 1970US Committee on Maternal Nutrition, citing the gain-to-birth-weight link, raises the target to 20-25 pounds for all women
  4. 1990IOM replaces a single figure with weight-gain ranges based on pre-pregnancy weight category
  5. 2009IOM/NASEM revises the ranges, aligns categories with WHO BMI cutoffs, and sets a specific range for obesity (still the standard in US practice)
  6. 2015CDC surveillance of full-term singleton births finds only about 32 percent of women gain within range; about 21 percent gain too little and about 47 percent too much
  7. 2017Goldstein and colleagues pool 23 cohorts and over 1.3 million women in JAMA, quantifying the risks of gaining above and below the IOM ranges

At a glance

Extra energy, 2nd tri
~340 kcal/day
Extra energy, 3rd tri
~450 kcal/day
Normal-BMI gain
25-35 lb
Breastfeeding
~500 kcal/day

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Weight Gain & Energy Needs. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources