After a few months on fat jabs such as Wegovy or Mounjaro, the feeling of suppression can start to wane and weight loss can stall, making it tempting to try the tricks being bandied about on social media before going up a dose. But is there any science behind these tricks and will they work?
Change the injection site
TikTok is awash with videos variously claiming that you will lose weight faster if you switch from injecting your tummy to injecting into your upper arm, your thigh, or switching from one arm to the other. Some even claim there can be ‘spot fat reduction’ if you jab the body part you want to target for fat-loss each week.
The official recommendation is to inject into fatty tissue on the abdomen, the outer thigh or the upper arm. But there is a growing belief across social media that some parts of your body work better than others and regularly switching could enhance the drug’s effectiveness and shift you off a stubborn weight-loss plateau.
Although there is no scientific evidence to back up any of these claims, some injection sites can be more effective than others – it depends on your distribution of fat.
The reason you inject into fatty tissue is specifically to slow absorption, so the drug’s effectiveness can be spread evenly across the seven days between injections. When injected into fat, the drug binds to proteins in the blood which act like a sponge or carrier, prolonging its life in the bloodstream and protecting it from being broken down or flushed out so quickly, so that it remains active in your system for days instead of hours.
According to Jason Murphy, the head of pharmacy at online pharmacist Chemist4U, ‘absorption can vary slightly depending on how much fat tissue you have in the injection area.’
He says the stomach often gives the most consistent uptake of medication because that is where most people carry a good layer of evenly distributed fat. Absorption is the same whether you have a lot of abdominal fat or a little.
But as you lose weight, you may find fat deposits shrink on your thigh and upper arm, making it more likely that injecting in those areas will hit muscle rather than fat.
Dr Dean Jones, a US obesity specialist and GLP-1 coach, warns that injecting into muscle could cause your weekly dose to be activated more quickly, perhaps triggering side-effects, and the benefits may not last as long.
‘Intramuscular injection does change absorption,’ he says. ‘It makes it faster and less predictable.’
So, if you have a good layer of subcutaneous fat on your upper arms or thighs, it won’t make any difference which of the three recommended sites you use – as long as you keep either rotating between these sites or slightly shifting where you stick the needle in each time.
Avoid targeting exactly the same small area each week as this can damage the tissue there, causing a scarring condition called lipohypertrophy which can impair absorption. This is why you are advised to avoid injecting too close to your belly button where fatty tissue can be patchy and where you may have scar tissue from piercings or past surgery which can lead to poor absorption.
Not only is the stomach often the best source of fatty tissue, but it is also easy to reach and rotate injection sites.
Change the day of the week you inject
There’s lots of chatter among Facebook support groups about the ‘best’ day to inject your jab, with influencers claiming that they fast-tracked their weight loss when they shifted to the beginning or the end of the week.
Most people seem to favour injecting on Fridays because it means you have full suppression to help resist the temptations of the weekend and also any side-effects (tiredness or nausea) won’t impact work.
However, others prefer to start each week with a Monday injection to keep them on track and to minimise the risk of a ‘Mounjaro kicking’ (nausea, heartburn or diarrhoea) which might be made worse by a weekend of food and drink bingeing.
Most users report suppression is strongest on days two to five so it makes sense to shift your jab timings to target your ‘toughest’ days each week when you gain most benefit from the suppression.
Murphy says that there is no ‘magic day’ to inject. ‘The most important message is consistency,’ he says. ‘The medication works best when your levels are kept steady week to week, so pick a day which works for you and stick with it.’
He stresses the importance of keeping the doses seven days apart. However, if you have a holiday planned and you are keen to jab before you go rather than take the injection pen with you, you can nudge your jab day forward one day at a time in the preceding weeks.
Change the time of day you inject
The TikTok chatter favours injecting in the evening so you can sleep off any nausea or fatigue side-effects, but the time of day won’t affect the jab’s effectiveness.
‘Your choice of timing comes down to how you respond to the injection,’ says Murphy. ‘It’s about finding the rhythm which suits your body and lifestyle.’
Pick a convenient time when you are most likely to remember your dose and you are not rushing or distracted. It doesn’t matter if your stomach is full or empty because the injections bypass the digestive system entirely.
