The Female Atlas sources: where our evidence comes from

Which guidelines sit behind each life stage?

It's normal to want to know where a health recommendation comes from. The main sources for each stage are below, and how we check facts explains the checking behind them.

Childhood. Food and feeding follow the Dietary Guidelines for Americans, 2025–2030, with SACN's 2018 report Feeding in the First Year of Life beside it for UK readers. Early peanut introduction rests on the LEAP trial (Du Toit et al., 2015), safe sleep on guidance from The Lullaby Trust and the AAP (2022), and sleep duration on the AASM recommendations for children (Paruthi et al., 2016). Activity for under-5s follows WHO's 2019 guidelines, alongside the UK Chief Medical Officers' Physical Activity Guidelines, 2019.

Puberty and adolescence. Bone building in the teenage years draws on Bailey et al., 1999, on bone mineral accrual around peak height velocity, the fastest point of the growth spurt, and on the National Osteoporosis Foundation position on peak bone mass (Weaver et al., 2016). Fueling for sport follows the IOC consensus on Relative Energy Deficiency in Sport (Mountjoy et al., 2023), and strength training follows the international consensus on youth resistance training (Lloyd et al., 2014). Activity levels come from the CDC Youth Risk Behavior Survey, 2023.

The reproductive years. Folic acid before pregnancy follows the USPSTF recommendation on preventing neural tube defects (2023), and PCOS care follows the International PCOS Guideline, 2023. Activity in pregnancy and postpartum draws on ACOG Committee Opinion 804 (2020), with Goom, Donnelly and Brockwell's 2019 guideline for returning to running after birth.

Perimenopause. Hormone therapy pages rest on The Menopause Society's 2022 position statement. Screening follows the USPSTF recommendations for breast (2024), colorectal (2021) and osteoporosis (2025) screening, and heavy and impact training for bone comes from the LIFTMOR trial (Watson et al., 2018).

Menopause. UK care follows NICE NG23, Menopause: identification and management, updated in 2024, beside the US position statement named above. Hormone therapy and breast cancer risk rests on the Collaborative Group on Hormonal Factors in Breast Cancer (The Lancet, 2019), and bone health for UK readers on the Royal Osteoporosis Society and NOGG osteoporosis guideline, 2022.

Postmenopause. Exercise for preventing falls rests on a Cochrane review (Sherrington et al., 2019), with NICE NG249 (2025) on falls assessment and prevention for UK readers. Exercise and osteoporosis follows the Royal Osteoporosis Society's 2019 consensus, Strong, Steady and Straight. Protein for older adults follows the PROT-AGE recommendations (Bauer et al., 2013), and dementia prevention follows the Lancet Commission (Livingston et al., 2024).

How do US and UK guidance differ on our pages?

It's common to find that US and UK advice don't quite match, and that's normal: different national bodies weigh the same evidence and reach slightly different schedules. In the US, guidance comes from bodies such as the US Preventive Services Task Force and the CDC; in the UK, from NICE, the NHS and UKHSA. Each page gives the US guidance first, with the UK guidance beside it.

Screening is the clearest example, because ages and intervals don't line up. For cervical screening, the US details come from the CDC's cervical cancer screening guidance, and the UK details reflect NHS England's 2025 change to the screening interval.

Everyday words shift across the Atlantic too. A Pap test in the US is a smear test in the UK, hot flashes are hot flushes, a mammogram is usually called breast screening, a primary care provider is a GP and a pediatrician is a paediatrician. Menopause hormone therapy is usually called HRT in the UK.

What kinds of evidence make up The Female Atlas sources?

Four kinds: guidelines, consensus statements, pooled analyses of many studies, and individual trials or long-running studies.

Guidelines carry the most weight, because a national or international body has weighed the whole field. The WHO Guidelines on Physical Activity and Sedentary Behaviour, 2020, appear in several chapters for that reason. Consensus statements gather expert agreement on a single question, as EWGSOP2 does for sarcopenia, the loss of muscle with age (Cruz-Jentoft et al., 2019).

Meta-analyses pool many studies to answer one question. Examples are menstrual cycle phase and exercise performance (McNulty et al., 2020), HIIT and abdominal and visceral fat (Maillard et al., 2018), and daily steps and mortality (Paluch et al., 2022). Single trials answer narrower questions, such as time-restricted eating compared with calorie restriction (Liu et al., 2022) and the TREAT trial of time-restricted eating (Lowe et al., 2020).

Long-running studies show how bodies change over years. The Study of Women's Health Across the Nation (SWAN) is behind what the menopause chapter says about how long hot flashes last (Avis et al., 2015), bone loss across the transition (Greendale et al., 2012) and cholesterol changes around the final period (Matthews et al., 2009).

Guidance also moves, so the year beside a source is worth a glance. Two recent entries are the US FDA's November 2025 labeling changes for menopausal hormone therapy and NICE's 2026 appraisal of fezolinetant for vasomotor symptoms of menopause.

Next steps

A good place to start is the life stage closest to where you are now, following any recommendation back to the guideline named beside it. It's common to find that a guideline doesn't quite describe your situation, and that's normal, because guidelines are written for large groups. When to see a doctor: if a symptom is new, worrying you or getting in the way of daily life, it's worth an appointment with your primary care provider (your GP in the UK) or OB-GYN, who can set the evidence beside your own history. Many women find it helpful to bring the name and year of the guideline with them. The evidence shows what helps most people, but it is not one size fits all, and what fits your body and your life is yours to decide.