“Ideal Weight”: Why There's No Single Number and What to Look at Instead

There’s no ideal weight you can work out from your height alone. The “ideal weight” tables and formulas came from life insurance data, and today clinicians use them for things like calculating some drug doses, not as health goals^[1,2]. Trials and guidelines look at other things: what percentage of your starting weight you lose, how your waist, blood pressure or blood sugar change, and whether you can keep the change. Here I explain where the idea comes from, which measures have more support, and why Saciedad doesn’t give you a target weight.

Where the idea of “ideal weight” comes from

US life insurers matched their policyholders’ weights against their mortality and published height-weight tables, including Metropolitan Life’s from 1959 and 1983. According to a review by Pai and Paloucek (2000), because those weights were linked to lower mortality, people started calling them “desirable” or “ideal.”^[2]

Then came formulas that estimate a weight from height. A review by Peterson and colleagues (2016) lists the main ones: Broca’s (1871), which subtracts a fixed amount from height in centimeters; Hamwi’s (1964), published in an American Diabetes Association text on diet; and Devine’s (1974), in an article on gentamicin therapy, an antibiotic. In 1983 new ones appeared, based on the Metropolitan Life tables and designed for drug dosing^[1].

Pai and Paloucek explain that this “ideal weight” came to be used as a stand-in for fat-free weight, and that the way some drugs behave in the body matched it^[2]. Peterson noted in 2016 that it’s still used to calculate drug doses and nutrient needs^[1]. It’s a clinical calculation tool, not a personal goal.

Why those numbers aren’t health goals

As early as 1985, a review in Annals of Internal Medicine warned that the lowest-risk weight differs between populations, between eras and depending on the cause of death. You can’t pin down an ideal weight for someone who differs from the groups the tables were built on, and some experts were already suggesting dropping the concept^[3].

Peterson adds that no single weight is best for every disease, age and ancestry, that the formulas give one number when the data support a range, and reports that compared with BMI they come out too low for shorter people and too high for taller ones^[1].

The Canadian obesity guideline (2020) offers a different idea: your “best weight,” the weight your body settles at when you keep up healthy habits. It may not match an “ideal” BMI, which the guideline acknowledges can be very hard to reach^[12].

What a “normal” BMI is, and isn’t

WHO classifies adults by body mass index (BMI: weight in kilograms divided by height in meters squared). In its Technical Report 894, 18.5 to 24.9 is the “normal range.”^[4] It’s a category for classifying and comparing populations.

The Lancet Diabetes & Endocrinology commission on clinical obesity (2025) says BMI should be used only for population studies and screening, not as an individual measure of health^[13]. Age matters too: in a meta-analysis of 32 studies with 197,940 people aged 65 or older, a BMI of 25 to 29.9 was not linked to higher mortality, and risk rose below 23^[5].

I go into this in BMI: what it measures and what it misses. The BMI calculator gives you your category, but on purpose it doesn’t calculate an “ideal weight” or a target BMI.

What the trials used as goals: percentages, not a finish-line weight

The studies in this table didn’t set a final weight. They measured how much each person’s weight changed from where they started, and what happened to their health.

Look AHEAD is an observational analysis inside a trial: it shows an association, not that each pound lost causes the improvement. Why results vary so much from person to person is in how much weight you lose on GLP-1s.

What guidelines say: the goal is health, not a number

• US endocrinologists (AACE/ACE, 2016). Their guideline aims treatment at weight-related complications and at body fat, to improve health and quality of life, with individualized goals^[10].
• European primary care guidelines (2019). The European Association for the Study of Obesity (EASO) guidelines say that losing as much as possible as fast as possible isn’t the key. Losing 5% to 10% is enough for substantial benefits, shrinking your waist matters even more than weight itself, and preventing regain is the cornerstone of treatment^[11].
• Canadian guideline (2020). Obesity care should aim for better health and well-being, not just weight loss^[12].
• Lancet commission (2025). In clinical obesity, the kind that already affects how organs work or daily life, the goal is to improve those problems, or put them into remission, and prevent further damage^[13].
• GLP-1 nutrition advisory (2025). Four US societies call for starting treatment with person-centered goals for both weight and health^[14].

Your waist and waist-to-height ratio

Your waist tells you something the scale can’t: how much fat sits around your abdomen. Since 2022 NICE, the UK body that assesses health care practice, has recommended that adults with a BMI under 35 measure their waist-to-height ratio and try to keep their waist to less than half their height^[15].

According to NICE, it works for both sexes, all ethnicities and people with a lot of muscle. The related risks are type 2 diabetes, high blood pressure and heart disease^[15]. How to measure: wrap the tape around your waist midway between the bottom of your ribs and the top of your hips, just above your belly button, after breathing out normally. Divide by your height in the same units. NICE’s example: 38 in ÷ 67 in = 0.57 (96.5 cm ÷ 170 cm)^[15].

Many clinics also use waist circumference cutoffs. The 2008 WHO expert report collects the most common ones^[16]:

The WHO report itself notes that the 94/80 and 102/88 cm cutoffs were given as an example, not as a formal WHO recommendation^[16]. The IDF adds that in the US the 102/88 cm values are likely to stay in clinical use^[17]. These are risk signals to discuss with your doctor, not targets to hit at any cost.

Body composition: what you lose, not just how much

The scale can’t tell fat from muscle. In the SURMOUNT-1 body composition substudy (summary), 160 participants had a DXA scan (which separates fat, lean mass and bone). About 75% of the weight lost was fat and 25% lean mass, with both tirzepatide and placebo^[18]. The 2025 advisory calls for assessing strength and body composition at the start, and for protecting muscle and bone with strength training and an adequate diet^[14]. More in protein and muscle on GLP-1s, and which scale or scan can track it in bioimpedance scale or DEXA.

Getting there is one part; staying there is another

The question “when do I stop?” often hides another one: what happens next. The withdrawal trials give a clue:

• Semaglutide. In the STEP 1 extension (summary), which followed 327 participants, those on semaglutide had lost an average of 17.3% and then stopped the drug and the lifestyle program. A year later they had regained about two-thirds of what they’d lost, and most cardiometabolic improvements drifted back toward baseline^[19].
• Tirzepatide. In SURMOUNT-4 (summary), after 36 weeks on the drug, those switched to placebo gained 14.0% over the next 52 weeks; those who stayed on it lost another 5.5%^[20].

The sources I cite don’t set a schedule for lowering, spacing out or stopping treatment once you reach a weight, and the 2025 advisory lists nutrition for weight maintenance after stopping as an area that needs more study^[14]. The full data are in what happens when you stop a GLP-1. If your weight has leveled off and you’re not sure whether it’s a plateau or your stopping point, see the weight-loss plateau.

When is enough? A decision with your doctor

Deciding you’ve arrived is a clinical conversation, not a number on the scale. These questions help you prepare for it:

• How have my blood pressure, blood sugar, lipids and the health problems I had changed?
• What does my waist, or my waist-to-height ratio, say?
• Am I keeping my strength, and eating enough and with variety?
• Can I hold this weight with the habits I have now?

You can take them with you using the doctor visit checklist.

Eating disorders are serious mental health conditions, and they can be treated^[22]. According to NIMH, early detection and treatment are important for a full recovery^[23]. If you recognize yourself in any of these signs, reach out to your doctor or a mental health professional.

Why Saciedad won’t give you a target weight

You won’t find one in any guide or tool on this site, and that’s not an oversight. There’s no correct number for your height, and your goal depends on things only the people treating you can see: your lab results, other conditions, medications and history. And a number can push you to eat less and less, when my rule is to treat satiety as a tool for eating well, not for eating as little as possible.

Frequently asked questions

How do I know my ideal weight?

No formula can tell you, because there isn’t a single number. It makes more sense to look, with your doctor, at how your health, waist and strength are changing, and at what weight you can keep with habits that work for you: what the Canadian guideline calls your “best weight.”^[12]

What is the ideal weight for my height?

There isn’t a specific one: height-weight tables came from insurance data^[2], and the lowest-risk weight changes with age, ancestry and disease^[3]. A BMI of 18.5 to 24.9 is a WHO category for classifying people^[4], not a personal weight, which is why I don’t publish a weight-for-height table.

What should my goal weight be on Ozempic or Zepbound, and when do I stop?

The trials didn’t set a finish-line weight: they measured percent lost and health. When it’s enough, and what to do about treatment, is something you decide with your prescriber. In STEP 1 and SURMOUNT-4, much of the weight came back after the drug was stopped^[19,20].

Do ideal-weight formulas like Broca, Hamwi or Devine work?

For clinical uses like calculating some drug doses, yes^[1,2]. As a health goal, no: they give a single number, ignore age and ancestry, and drift off depending on height^[1].

How much weight do I need to lose to see health benefits?

In studies, losing 5% to 10% of starting weight was linked to better blood sugar, blood pressure and lipids^[7,11], and in the Diabetes Prevention Program the 7% goal cut the number of new type 2 diabetes cases^[6]. What change makes sense for you is something your doctor weighs up.