Clothes and Sizes While Losing Weight on Ozempic, Wegovy or Zepbound: When to Buy and How Not to Overspend

On semaglutide (Ozempic, Wegovy) or tirzepatide (Zepbound, Mounjaro), your size changes over many months, not all at once. In the trials, the waist shrank by about 1.5 inches for every 10 pounds lost, on average, and most of the change came in the first 5 to 8 months. After that, loss slows until it levels off. Nobody has studied how many clothing sizes people drop: what we have are waist measurements. My way of reading it: buy little and cheap while your body is changing, and save the big purchases for when your weight has been stable for a while.

What the trials measured: waist inches, not sizes

The STEP 1 and SURMOUNT-1 trials measured waist circumference as well as weight^[1,2]. It’s the closest thing we have to a pants size. Here are the averages:

On medication, the ratio comes out fairly similar: about 1.4 to 1.6 inches per 10 pounds (0.8 to 0.9 cm per kg). But that’s a group average. In the placebo groups, who lost little, the waist shrank by more than 2 inches per 10 pounds^[3,4,9]. With small losses, an inch of measuring error counts for a lot. And every body loses from different places. Treat it as a rough guide, not a forecast.

What exactly is lost? In the SURMOUNT-1 body-composition substudy, which measured 160 people with a DXA scan, about 74% of the weight lost on tirzepatide was fat and 26% lean mass^[5]. To protect muscle, see protein and muscle on a GLP-1 and strength training.

How fast sizes change

Most of the change comes early:

• Semaglutide. In STEP 4, people who completed 20 weeks of treatment and reached 2.4 mg had lost 10.6% on average^[6]. Those who stayed on it lost another 7.9% over the next 48 weeks^[6].
• Tirzepatide. In SURMOUNT-4, the 670 participants who completed the first 36 weeks had lost 20.9%^[7]. Those who stayed on the drug lost another 5.5% over the next 52 weeks^[7], and their waist shrank another 4.3 cm (1.7 in)^[4].

In waist terms, that’s about 0.8 inches a month over the first 8 months on tirzepatide, and much less afterward (my math from the label figures^[4]). If you buy jeans that fit just right in month 2, they may well be loose by month 4.

Then comes the plateau. In an analysis of SURMOUNT-1, half the people who stayed on treatment and lost at least 5% leveled off by about weeks 24 to 36, depending on their starting BMI. By week 72, 87.6% to 90.2% had reached a plateau. It came somewhat later for women^[8]. For semaglutide, in the STEP 5 trial, the EU prescribing information says mean body weight decreased through week 68, after which a plateau was reached^[9]. I go into more detail in the GLP-1 weight plateau and how much weight you lose.

Where it shows first: waist, hips and chest

It depends on where your body stores fat. According to a 2012 physiology review, at the same total body fat, women carry more fat under the skin of the belly, hips and thighs, and less visceral fat (the fat around the organs) than men. But it isn’t a rule: about 40% of women aged 30 to 79 store fat mainly around the belly^[10].

Visceral fat tends to go first, proportionally. In a systematic review of 61 studies, modest weight loss reduced visceral fat more than belly fat under the skin; with larger losses, that edge faded^[11]. In the SURMOUNT-1 substudy, visceral fat fell 40.1% on tirzepatide, against 21.3% for total body weight^[5]. The EU prescribing information for Wegovy also says the drop in total fat mass was accompanied by a reduction in visceral fat^[9].

My reading: it makes sense that your waist would be one of the first places you notice, especially if you carry weight around your middle. Hips and thighs may move at a different pace. But no GLP-1 study has measured the order in which sizes change for each type of garment.

Bras are similar. In a 2017 study of 80 women who had bariatric surgery, breast volume fell by 39.4% on average on mammograms taken about 10 months after surgery^[14]. That’s a different population, with more weight loss than the average on medication, but it suggests bra size can change a lot too. Getting refitted every few months saves buying blind.

When and how to buy without overspending

There are no studies here: these are practical ideas.

1. Measure instead of guessing. The NHLBI, part of the National Institutes of Health, says to measure your waist standing, with the tape just above your hipbones, right after you breathe out^[12]. Write down your hips and chest too, once a month, and compare them with the size chart for the item.
2. Buy in stages. While you’re losing, get a few basics that will last you some weeks: a couple of pairs of pants, some underwear and whatever you wear every day.
3. Favor things that adjust. Elastic or drawstring waists, wrap styles, fabrics with some stretch and belts with plenty of holes cover more than one size.
4. Alter what you love. A tailor can take in a waist or a leg. Ask first whether the garment allows it: not all have room.
5. Thrift and swap. Buying secondhand, or trading clothes with family and friends whose sizes are also changing, costs far less than buying new at every stage.
6. Invest once your weight settles. The good coat, the suit or the expensive shoes can wait until you’ve been at a stable weight for a few months.

There’s one caveat on point 6. In the STEP 1 extension, people who stopped semaglutide regained about two-thirds of the weight they had lost within a year^[13]. In SURMOUNT-4, those switched to placebo regained 14.0% of their weight over 52 weeks^[7], and their waist grew 7.8 cm (3.1 in)^[4]. That isn’t a prediction for you; whether to stay on treatment is a decision you make with your prescriber. But it explains why some people hang on to a few in-between pieces. I cover it in stopping a GLP-1 and weight regain and maintenance at goal weight.

The mirror lags behind the tape measure

Some people take a while to see themselves differently, even when the tape and their clothes say otherwise. I haven’t found solid studies that measure that lag on GLP-1 medications. The closest are two reviews, both with caveats. In a 2015 meta-analysis of seven studies, almost all in women, weight loss programs improved body image more than the comparison group in four studies, but not in the other three^[15]. After bariatric surgery, a review of 60 articles found improvements in some aspects of body image but concluded that little research has been done^[16].

Something practical: your logged measurements and the clothes that no longer fit are data that don’t depend on how you see yourself on a given day. If you’re noticing other changes the scale doesn’t show, like thinking less about food, I explain that in food noise. And if worry about your body leads you to eat much less than you need, bring it up with your doctor.

Loose skin and shapewear: a separate question

Clothes that are too big and skin that’s left over are different problems. New clothes don’t change your skin, and loose skin isn’t fixed by a smaller size. What’s known about loose skin, what helps and what doesn’t, is in loose skin after weight loss. There I note that I haven’t found studies showing that shapewear or compression garments prevent or reduce loose skin. Whether to wear them for comfort is a personal choice.

What to do with clothes that no longer fit

The options are the usual ones: alter them, sell them, donate them or pass them on. Some people clear everything out the moment it stops fitting, and some keep one piece from where they started, as a keepsake or a reference. It’s a personal choice and neither option is better. Keep the earlier caveat in mind: if you’re thinking of getting rid of every in-between piece, you may want to wait until your weight has been stable for a while.

FAQ

How many pant sizes will I drop for every 20 pounds?

Nobody has measured it in sizes. Using the trial averages, 20 pounds less works out to about 3 inches off the waist^[3,4], but for any one person it can be quite a bit more or less. How many sizes that is depends on each brand’s size chart, and they aren’t the same. The most reliable approach is to measure yourself and check the chart for the item.

Should I wait until I reach my goal weight to buy clothes?

You don’t have to wait for everything. Everyday basics can be replaced in stages, with inexpensive, adjustable or secondhand pieces. For bigger purchases, a reasonable time is when your weight has been stable for a few months. Keep in mind that the plateau doesn’t always land at the number you had in mind^[8].

When will I notice a change in my size?

In the trials, most of the weight came off in the first months: 10.6% at 20 weeks on semaglutide in STEP 4^[6] and 20.9% at 36 weeks on tirzepatide in SURMOUNT-4^[7]. When you notice it in your clothes depends on your starting point and where you lose first.

Does bra size change too?

It can. After bariatric surgery, breast volume fell by 39.4% on average in a study of 80 women^[14]. It hasn’t been measured on GLP-1 medications. Getting refitted every few months is the simplest way to know.