Why the second trimester adds about 340 calories
You don't need to 'eat for two.' Here's why pregnancy energy needs rise by about 340 calories a day in the second trimester — and 452 in the third — and where the numbers come from.
Pregnancy is the original “eating for two” story — and it’s mostly a myth. Your body does need a little more energy as pregnancy goes on, but a little is the key word. Here’s what actually changes, and why.
How many extra calories do you need in pregnancy?
In the first trimester, you need no extra calories at all. In the second trimester, energy needs rise by about 340 calories a day, and in the third by about 452 a day. Those figures come from the Institute of Medicine’s Dietary Reference Intakes for Energy (2005) — the reference standard clinicians use — and they describe additions to your usual intake, not a brand-new total.
Why the second trimester specifically?
Because that’s when your body starts doing noticeably more building and more work. The 2005 estimate is the sum of two parts: about 180 calories for the energy laid down in your baby, placenta and your own tissue, plus about 160 calories for the extra energy your body now expends. Add them and you get roughly 340 calories a day in the second trimester.
The third-trimester figure rises to about 452 not because more tissue is being deposited — that part stays around 180 — but because the energy you expend keeps climbing as the pregnancy advances (roughly 272 calories by then). So the increase is gradual, not a switch that flips.
What does 340 calories actually look like?
Not much. ACOG describes it as roughly a glass of milk plus half a sandwich. This is why the guidance everywhere — from ACOG to the NHS — is quality over quantity: nutrient-dense foods (protein, fruit and vegetables, wholegrains, dairy) matter far more than bigger portions. You don’t need to hit the number at every meal; balance across the week is enough.
Do twins mean twice the calories?
No. Even a multiple pregnancy doesn’t approach “a second adult.” ACOG puts twins at roughly +600 calories a day and triplets at +900 in later pregnancy — still well under double. “Eating for two” simply isn’t how the maths works.
Can you have too much?
Yes. More energy isn’t safer. Eating well beyond your needs can drive excess gestational weight gain and raise risks like gestational diabetes, without benefiting you or your baby. And these figures are population averages, not universal targets — needs vary by body, and some people (including those carrying more weight) may need less. Guidance also varies: the NHS, for instance, frames the rise as modest and mostly in the final months.
The honest takeaway: your body is building something remarkable on a surprisingly small energy budget. Nourish it well — you don’t need to double it.
This is general information, not medical advice. Your midwife, doctor or dietitian can tailor guidance to you.
References
- Institute of Medicine — Dietary Reference Intakes: Energy (2005)
- ACOG — Nutrition During Pregnancy
- NHS — Have a healthy diet in pregnancy
General information, not medical advice. Reviewed for accuracy; always consult a qualified professional about your health.
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