There is no current evidence showing a consistent gender difference in weight-loss outcomes with tirzepatide (Mounjaro®) or semaglutide (Wegovy®). Clinical trials report overall average weight-loss percentages (e.g., up to ~20%) for both men and women, but individual results do always vary. 

The opposite is often the case. Emerging research suggests that anti-obesity medications including GLP-1 agents, like those in weight loss injections, may increase testosterone levels in some men with obesity or type 2 diabetes. It should be noted that this is still early research, and individual monitoring remains important.

There is not currently any evidence of weight loss injection side effects that are specific to men and don’t affect women taking the same medication. The common side effects (nausea, gastrointestinal symptoms, risk of pancreatitis) can be experienced by anyone taking weight loss injections. Most side effects usually go away once the body adjusts to the medication and dose.

Generally, men aged 18+ with obesity (BMI criteria as per NHS/privately) and weight-related health conditions may be eligible for a prescription. However, not everyone is suitable for taking weight loss injections and a full assessment must always be carried out by a qualified UK prescriber before you start taking this medication. 

Clinical trials indicate that men taking Mounjaro® can lose somewhere between 5%-20% of their body weight, over a period of up to 18 months. It’s important to note that everyone responds uniquely to medication and actual results depend on adherence, starting weight, fitness, muscle mass, metabolic health and lifestyle.

It’s essential for men taking weight loss injections to use them in combination lifestyle changes, such as high levels of activity and a balanced diet. Maintaining these healthy habits will help to sustain the weight loss achieved and not regain it if you stop taking the medication. 

Rapid weight loss can affect both fat and muscle. Men using Mounjaro® or Wegovy® may notice changes in strength or exercise performance, especially if appetite has reduced significantly.

To protect muscle during weight loss treatment:

• Eat enough protein throughout the day

• Lift weights or use resistance training to maintain strength

• Talk to your trainer (if you have one) about adjusting your routine

• Give your body time to recover between sessions

• Avoid skipping meals

Most men find that as body weight drops, body composition improves even if absolute strength changes slightly.

It can be more challenging! This is often due to changes in metabolism, stress, lifestyle and hormone levels. Weight loss injections, combined with activity and a balanced diet, can help support progress at any age.

Many men with obstructive sleep apnoea carry extra fat around the neck and abdomen, which can make the airway narrower and breathing harder at night. As weight comes down - especially visceral fat - the pressure on the airway often reduces too. This is why some men may notice they snore less, wake up fewer times and feel more awake during the day once they’ve been on Wegovy® or Mounjaro® for a while.

It’s not a guaranteed fix for everyone, and it doesn’t replace your usual sleep apnoea treatment, like CPAP (so it’s important to keep using them). But losing weight can make a real difference to how well you sleep and how refreshed you feel. If you have sleep apnoea, always consult with your GP or sleep specialist as you go, so they can guide you safely as things hopefully improve.

There’s no evidence that Wegovy® or Mounjaro® harm male fertility. In fact, for some men, improving overall health and reducing excess weight can have a positive impact on things like testosterone levels, energy and general wellbeing, which all play a role in reproductive health.

If you’re having fertility checks or you and your partner are trying to conceive, it’s worth mentioning this to your prescriber so they can give advice based on your individual health and any other medications you’re taking. But for most men, these injections don’t cause fertility problems and may even support better hormonal balance over time.

If you are training or aiming in your gym activity to build or maintain muscle, there are some important considerations if you’re thinking of starting weight loss injections. 

• Appetite may reduce, so ensure your diet includes enough protein to preserve muscle.

• Because you lose fat mass, your body weight may reduce and possibly strength/performance in absolute terms will adjust. Body composition should improve. 

• Monitor your fatigue after workouts or training sessions to ensure recovery and speak to your trainer about adjusting load and nutrition.