Weight loss injections — experiences

What happens month by month

A programme with GLP-1 injections proceeds in phases that are remarkably consistent. The first 4 weeks are an adjustment period — appetite already drops, but weight loss is limited because the dose is still low and side effects are at their strongest.

From months 2-3 the dose reaches an effective level and weight drops at a pace of 2-4 kilos per month on average. From month 6 the pace slows to roughly 1-2 kilos per month. By month 12, the majority of the eventual weight loss has been achieved.

The picture varies enormously per individual: 5% to 25% of body weight. The average with good adherence is around 12% in a year — substantially more than diet alone (3-5% on average).

Realistic weight loss per medicine

Not every medicine works equally strongly. Tirzepatide (Mounjaro) is the strongest for average weight loss, followed by semaglutide (Wegovy/Ozempic), then liraglutide (Saxenda). Which medicine suits you depends on BMI, comorbidity, tolerance of side effects and costs.

Side effects in weeks 1–4 — what to expect

The first 4 weeks are the toughest in terms of side effects. What patients in our clinic report most often:

Nausea (40-60% of people): especially in the evening, in the first week after a dose increase. Tips: smaller meals, no fatty food on the day of the injection, drink enough.

Gastrointestinal complaints (20-30%): constipation or, conversely, diarrhoea. Fibre + 2 litres of water a day help. With constipation lasting >5 days: call your doctor.

Heartburn (15-20%): avoid lying down for long periods after eating, eat your last meal 3 hours before bedtime. For severe symptoms, a proton pump inhibitor can be prescribed for a short period.

Tiredness and headache (10-20%): often related to calorie restriction. Make sure you get enough protein (1.2-1.6 g/kg) and drink water.

With sharp upper abdominal pain, persistent vomiting (>2 days), or jaundice: contact your doctor immediately. This can indicate pancreatitis or gallstones — rare but serious.

Patterns of success vs. patterns of failure

From clinical data and our own experience, five patterns stand out that make the difference between strong results and disappointment.

• SUCCESS: treating it as a medical programme, not a 'miracle pill'. People who trust their doctor and take the coaching seriously achieve 2-3× better outcomes.
• SUCCESS: strength training from week 4. Protects muscle mass during rapid weight loss, prevents metabolic adaptation, helps against yo-yo.
• SUCCESS: higher protein intake (1.2-1.6 g per kg of body weight). Keeps you full longer, preserves muscle mass, speeds up recovery.
• FAILURE: speeding up dose titration 'because it's going too slowly'. Causes stronger side effects without extra weight loss, often leads to stopping early.
• FAILURE: simply carrying on drinking alcohol. Leaving aside the bupropion interaction, alcohol intensifies nausea, adds empty calories and disrupts sleep.

Four common types of experience

Below are four representative patient journeys that we often see in our clinic (anonymised, composed from multiple patient stories).

1. 'It just happened' — woman, 42, BMI 32. Starts Wegovy, loses 14 kilos in 9 months. Side effects mild, appetite significantly dampened. Works mainly because she had long been looking for a tool that broke through the feeling of hunger.

2. 'Plateau in month 4' — man, 51, BMI 35. Starts Mounjaro, loses 10 kilos in 3 months, then 8 weeks of standstill. Broken through with a dose adjustment and strength training coaching; eventually 22 kilos in 14 months.

3. 'Couldn't tolerate Mounjaro, but could tolerate Wegovy' — woman, 38, BMI 30. Severe nausea on tirzepatide 7.5 mg, switch to semaglutide. Slower pace but much better tolerated. 11% weight loss in 12 months.

4. 'Stopped deliberately' — man, 47, reached BMI 28 after 9 months. Does not want long-term medication. Tapers off over 6 weeks under coaching, keeps up strength training and protein intake. Maintains 80% of the result after 18 months.

When is it not for you?

GLP-1 injections are not one-size-fits-all. In the following cases we advise an alternative intervention or a different medicine:

• Pregnancy, breastfeeding or an active wish to become pregnant within 2 months
• Personal or family history of medullary thyroid carcinoma or MEN-2 syndrome
• History of acute pancreatitis
• History of severe eating disorders under active treatment
• BMI <27 without comorbidity (no medical indication)
• Untreatable gastroparesis
• Inability or unwillingness to make the accompanying lifestyle changes

Anti-yo-yo: what after the first 12 months?

The big risk with GLP-1 medication is weight regain after stopping. STEP-4 (semaglutide) showed that ~67% of the lost weight comes back within 12 months without a replacement strategy.

Our approach: from month 6 the anti-yo-yo phase actively begins. That means intensifying strength training, keeping protein intake high, embedding eating patterns in daily routines. After that, tapering can take place in consultation with the doctor — not stopping abruptly.

For those for whom long-term use is not desirable (e.g. because of side effects or costs): plan a structured tapering protocol over 4-12 weeks with your doctor, combined with intensive lifestyle coaching.