Doctor reveals exactly what happens to your body in first four weeks of taking weight-loss jabs

A medical professional has lifted the lid on exactly what happens to the human body within a matter of weeks of taking weight-loss jabs.

Millions of people worldwide, including dozens of Hollywood's rich and famous, have turned to GLP-1 medications to help them lose weight and keep obesity at bay.

In the US, a staggering one in eight adults, approximately 12 per cent of the population, have turned to drugs like Wegovy and Mounjaro, which shed the pounds by suppressing appetite and regulating blood sugar levels.

While the verdict in the battle of the best is yet to be determined, a doctor has revealed what a patient might expect in a typical four-week period while on the medication.

Week one - Mounjaro vs Wegovy

In the first week on Mounjaro, patients usually take the lowest dose (2.5mg) which Doctor Crystal Wyllie at ZAVA says is for good reason, serving as an 'adjustment period' for the body to acclimatise to it.

In this time, patients might face some common side effects, like nausea, diarrhoea or constipation.

Side effects are common in the first week (Getty)

Meanwhile, those starting out on Wegovy receive an initial dose of 0.25mg, which the doc says might cause you to notice a slight change in appetite, such as feeling fuller for longer, and advises reducing food intake.

Week 2 - slight changes on the scale

In the second week, Dr Wyllie says there are 'more obvious appetite changes' on Mounjaro.

"You may find yourself eating less and staying fuller for longer. It is important during this stage to stick to your diet and exercise plan," she added.

As for those on Wegovy, the expert noted the increase in dosage should make you feel your appetite go down even further and you may even experience some 'small changes' on the scale.

Week 3 - side effects kick in

In the case of both medications, the expert says week three can be particularly tough for those pesky reported side effects and advises sticking to small, plain meals and increasing water intake if the nausea is strong.

"Be sure to see a doctor for any vomiting and severe abdominal pain to rule out serious causes," she added.

Finally, you're likely to see some noticeable changes in your physique by week four (Getty)

Week 4 - body weight loss

Finally, the good news we've all been waiting for: Dr Wyllie said it's likely you'll experience a change in your physique or at least the number on the scale by week four.

According to a study by ZAVA, patients lose on average four per cent of their starting body weight on Mounjaro in the first month, or around two per cent on Wegovy.

However, as the dosages increase and over a longer period of time, the expert points out that Mounjaro helped patients lose an average of 22.5 per cent of their starting weight over the course of 72 weeks, while Wegovy typically sees patients lose around 17 per cent.

How to get the best results on Mounjaro and Wegovy

According to the medic, several factors can affect how much weight a patient can lose on the drugs, including age - bringing about a slower metabolism and changes to hormones, as well as diet and exercise.

Both drugs work best when supported with a healthy diet and an active lifestyle, she stressed, and these changes have to be sustainable to support and maintain your new size when you come off the medication.

She also advised sticking to the dosage schedule, which includes taking the injections at the same time every day.

"Losing weight with weight loss injections is not an overnight process, and it can take time to see results," she concluded. "While some see significant weight loss changes within their first month, for some, the desired result takes longer. It is crucial to make healthy lifestyle changes to support your weight loss process."

A spokesperson for Eli Lilly told UNILAD: "Mounjaro (tirzepatide) should only be used when prescribed by a licensed healthcare professional, and prescriptions should be fulfilled and supplied by registered pharmacies or providers. We encourage patients to consult their doctor or other healthcare professional to discuss any possible side effects they may be experiencing and to ensure that they are getting genuine Lilly medicine."

A spokesperson for Novo Nordisk told UNILAD, in part: "In the UK, Wegovy is indicated as an adjunct to a reduced-calorie diet and increased physical activity for weight management and cardiovascular risk reduction. In adults, the maintenance dose of Wegovy is 2.4 mg once weekly. Ozempic (semaglutide injection) is licensed for the treatment of type 2 diabetes – it is not licensed for weight management.

"We recommend patients take these medications for their approved indications and under the supervision of a healthcare professional. Treatment decisions should be made together with a healthcare provider who can evaluate the appropriateness of using the medicines based on assessment of a patient’s individual medical profile.

"Patient safety is of the utmost importance to Novo Nordisk. We continuously collect safety data on our marketed GLP-1 RA medicines and work closely with the authorities to ensure patient safety. As part of this work we continue to monitor reports of adverse drug reactions through routine pharmacovigilance."