Why does Foundayo make some people feel tired?
Foundayo can make us feel tired by reducing hunger levels to such an extent that we don’t eat enough. It may also be connected to common side effects of Foundayo such as vomiting and diarrhoea.
These effects can prevent our body from getting enough energy and nutrients to support essential bodily functions.1,2,6
On average, adults need roughly 2000-2500 calories per day.
During weight loss on Foundayo, we’ll be eating less, potentially 1500-1750 calories per day.
To support essential functions, the body will use its fat stores to provide sufficient energy when we eat in a calorie deficit.
However, if we eat too little, say less than 1500 calories per day, the brain may respond by essentially ‘slowing things down’ to preserve its energy stores, as it perceives very low energy intake as a threat to survival.
This ‘slowing down’ is what makes us feel tired. The brain’s top priority is always our survival, so in this scenario, it’s doing its job, and isn’t necessarily a sign that anything is wrong.
A simple solution to very low energy intake is to eat more. This may feel challenging on Foundayo if it’s reduced your appetite and desire for food, but we’ll discuss practical solutions to this below.
Other possible causes of fatigue and tiredness on Foundayo include low blood pressure, low blood sugar with certain diabetes treatments, and poor sleep.
Researchers are also studying how Foundayo and similar GLP-1 medications affect sleep and behaviour through the brain.1,3,4,5
How to eat enough on Foundayo
Foundayo can reduce appetite to such an extent that we eat too little and don’t get the sufficient energy and nutrients we need. It mimics the function of GLP-1, a hormone that helps regulate appetite and blood sugar.1,2
The medication reduces hunger and food noise, and slows how quickly our stomach empties. We may feel full more quickly, and side effects like nausea can make eating less appealing.1,2
First, if you’re experiencing extremely low appetite and struggling to eat, we recommend contacting your prescriber immediately to discuss your options, as you may need to reduce the dose of the medication.
But there are also lifestyle changes you can make that can ensure you’re eating enough on Foundayo.
Here are a few of our top tips on how to ensure you’re eating enough on Foundayo, even when your appetite is significantly lower than usual.
1 – Maintain regular mealtimes
Aim for 3 balanced meals a day based mainly on whole foods, with a protein-rich snack between meals if needed.
Maintaining the habit of eating breakfast, lunch, and dinner can support our eating habits and nutritional needs without relying on hunger to remind us to eat.
We’d recommend meal planning and batch cooking to minimise the stress around food choices at every meal.
If you keep freshly made meals in the fridge or freezer for lunch at work or to warm up in the evening when you don’t fancy cooking, you’ll create an environment that supports your health without having to think about what to cook all the time.
2 – Build meals around protein and whole foods
We recommend eating a diet based primarily on whole foods that contains enough protein, fibre, fat, and complex carbohydrates, and limits ultra-processed foods.
Protein helps maintain muscle mass during weight loss as well as having an essential role in our immune system.2
Chicken, fish, eggs, Greek yoghurt, tofu, tempeh, cheese, red meat, and game all provide high-quality protein.
We recommend a protein portion about the size of your palm at each meal.
Plant-based protein sources such as lentils, beans, and nuts provide protein, but individually they don’t contain enough of the essential amino acids our bodies need, so we recommend combining plant-based proteins in your meals if you’re a vegan.
Complex carbohydrates provide a vital energy source for the body. Whole-food sources such as rolled oats, potatoes, brown rice, wholegrain bread, beans, and lentils also provide fibre and other nutrients.2
We recommend including a fist-sized portion of complex carbohydrates in every meal, or roughly 25% of your plate.
Balanced meals across the day could include:
Our Foundayo meal plan gives more examples of balanced meals when using GLP-1 medications.
3 – Cook, prepare, and eat easier-to-digest foods
Chopping, dicing, or mincing ingredients before cooking them makes foods significantly easier to eat and digest.
These processes also help our body extract vital nutrients from vegetables, nuts, and seeds that might otherwise be bound to the fibre in plant foods.
Some examples of foods and recipes we’d recommend eating when you’re struggling to eat enough:
- Scrambled eggs instead of boiled, fried, or poached
- Minced beef instead of whole cuts
- Diced chicken instead of a whole chicken breast
- Diced or grated tofu instead of whole cuts
- One-pot dishes like casserole, chilli, bolognese, and stews where the foods are much softer after cooking for a long time in a sauce
- You can also add a scoop of protein powder to smoothies and soups
Vomiting and diarrhoea can cause dehydration
Vomiting and diarrhoea can make us tired by causing fluid and mineral loss. If we can’t drink enough to replace the fluid we’re losing, we can become dehydrated.6
Alongside tiredness, dehydration can cause dizziness, dark urine, and less frequent urination.
Foundayo’s prescribing information also warns that dehydration from these side effects can affect how well our kidneys work.1,6
We recommend drinking a glass of water immediately after waking up, keeping a drink nearby and having a glass of water with meals.
If you’re feeling nauseated and struggling to drink at all, start with small sips and gradually drink more as you can manage it.6
If you’re losing fluid through vomiting or diarrhoea, ask a pharmacist about an oral rehydration solution. These replace lost fluid and salts, and the pharmacist can recommend a suitable product.6
Ask for an urgent GP appointment or contact NHS 111 if urine becomes dark, you’re passing less urine, or dizziness when standing doesn’t go away. Get urgent advice if vomiting means you can’t keep fluids down.6
Our Foundayo side-effects guide explains digestive symptoms and when to get medical help.
Could Foundayo’s effects on the brain cause tiredness?
Foundayo’s effects on the brain may also contribute to feelings of fatigue. The parts of our brain that control appetite also influence how awake we feel and how motivated we are to be active.3,4
Changes in wakefulness
Hunger drives us to seek food, and the brain coordinates this with wakefulness. Animal research shows that activating hunger-sensitive brain cells increases wakefulness, while reducing their activity allows hungry animals to sleep more normally.8
Our interpretation is that Foundayo’s sustained signal to reduce hunger could also reduce some of the wakefulness associated with seeking food. This would help explain feeling sleepier or less alert, even when we’re eating enough.
A 2023 study supports this theory. Rats given liraglutide, another GLP-1 medication, slept more during the hours when they would normally be active, showing that GLP-1 treatment can influence sleep and wakefulness as well as appetite.3
Changes in motivation and effort
GLP-1 medicines also influence dopamine, a chemical messenger that helps our brain judge whether an activity is worth the effort and supports our drive to pursue it.
A 2026 study found that orforglipron, the drug in Foundayo, activated a brain pathway that reduced dopamine signals associated with eating rewarding food in mice.4
If changes in these motivation systems extend beyond food, everyday activities could feel harder to start and sustain. We might describe this as having less energy, even without feeling the need to sleep.
A 2025 mouse preprint provides evidence for this wider effect. Mice given semaglutide ran less than untreated mice given the same amount of food, and also worked less to gain access to a running wheel.9
Because both groups ate the same amount of food, eating less couldn’t explain why the mice given semaglutide ran less, suggesting there was something about the medication’s effect that led to their reduced activity.9
These are plausible explanations drawn from animal research. Whether these effects occur in humans taking Foundayo hasn’t yet been established.
Still, we can take practical steps to improve our energy levels and reduce tiredness by getting better sleep, staying active in ways we can manage, eating enough, and staying hydrated.2,5
Keep regular sleep and wake-up times
Going to bed and waking up at similar times each day can help us get enough sleep and feel more rested during the day.5
Our top tips to improve sleep are:5
- Avoiding caffeine after midday
- Keeping the bedroom dark, quiet, and comfortable
- Reducing screen use in the hour before bed
- Avoiding stimulating activities before bed (like gaming), and doing calming activities like reading, listening toa
Staying active while feeling tired
Over time, regular activity helps our muscles build more mitochondria, the parts of our cells that use oxygen to release energy from food.10 This improves our muscles’ ability to keep working, so everyday activities start to feel easier.
We recommend choosing a type of movement you enjoy, such as walking, swimming, cycling, or dancing, and making it part of your routine.
For example, you could plan a 10-minute walk after breakfast or dinner. Once that feels comfortable, extend the walk by five minutes or add another short walk later in the day.
If getting started feels difficult, arrange to walk with a friend or family member at a set time. Having someone to meet gives us a plan to follow when motivation is low.
Building strength at home
Strength exercises help maintain muscle during weight loss, and we can start at home without gym equipment.2 Examples include:
- Standing up from a sturdy chair and sitting back down slowly
- Doing press-ups against a wall
- Raising your heels and lowering them slowly while holding a kitchen worktop for support
You could start with five slow repetitions of one exercise after brushing your teeth or while waiting for the kettle to boil. Choose a point in your routine when you’re likely to remember and have time to do it.
If tiredness comes with dizziness, weakness, or feeling faint, speak to your prescriber before exercising.
Other medicines can contribute to tiredness
Some diabetes and blood-pressure medicines may need adjusting when taken alongside Foundayo. Some combinations can lower blood sugar or blood pressure too much, causing symptoms that may include tiredness.1
Insulin and some diabetes tablets
Foundayo can increase the risk of low blood sugar when taken with insulin or a sulfonylurea. Insulin is the hormone that helps move sugar from our bloodstream into cells that use it for energy.1
Sulfonylureas are diabetes tablets that make the body release more insulin. Adding Foundayo to either treatment can further lower blood sugar, so you may need to reduce the insulin or tablet dose.1
If you experience shaking, sweating, or hunger, check your blood sugar if you’ve been advised to monitor it. Follow your diabetes team’s instructions for treating low blood sugar.
Tell your diabetes team or prescriber if low readings or symptoms keep happening. They can adjust treatment if needed; don’t reduce or stop insulin yourself.
Blood-pressure medicines
Low blood pressure can occur while taking Foundayo, particularly alongside medicines that lower it. Fluid loss from vomiting or diarrhoea can contribute too.1,6
If you keep feeling dizzy or faint when standing up, ask your prescriber to check your blood pressure and medicines. Bring any readings you already take at home.
Your prescriber can decide whether you need to change your treatment. Seek urgent advice if dizziness when standing doesn’t go away.6
When to speak to your prescriber or GP
Speak to your prescriber if tiredness is severe, isn’t improving, or affects everyday activities such as working or looking after yourself. Arrange a GP appointment if tiredness lasts for a few weeks and has no clear cause.5
Other symptoms can help your clinician decide what to check. For example, tiredness with vomiting may suggest dehydration, while tiredness with shaking and sweating may suggest low blood sugar.1,6
| What else is happening? |
Possible explanation |
What to check or do |
| Meals have become much smaller or are regularly missed |
Not getting enough food and nutrients |
Ask your dietitian or nutritionist to check whether meals provide enough food and nutrients |
| Vomiting, diarrhoea, dark urine, or passing less urine |
Dehydration from fluid loss |
Ask for urgent GP advice or contact NHS 111 for dark urine, reduced urine, or difficulty keeping fluids down |
| Dizziness or feeling faint when standing |
Low blood pressure, fluid loss, or another cause |
Ask your prescriber to check your blood pressure and medicines; seek urgent advice if dizziness when standing doesn’t go away |
| Shaking, sweating, or hunger, particularly when taking insulin or certain diabetes tablets |
Low blood sugar |
Follow your diabetes team’s advice for treating low blood sugar, and tell them if it keeps happening |
| Tiredness continues despite regular meals, fluids, and rest |
A medication effect, sleep problem, or another health condition |
Make an appointment with your prescriber or GP |
Before the appointment, note when tiredness started, your Foundayo dose, and whether it worsened after you increased it. Include changes in eating, drinking, sleep, or mood, and any other symptoms.
Your GP may arrange blood tests to check for causes such as thyroid problems or iron deficiency anaemia, where low iron reduces the blood’s ability to carry oxygen.5
A nutrient deficiency found soon after starting Foundayo may have developed before treatment began. If a deficiency is confirmed, your GP can recommend an appropriate supplement or other treatment.2,5
Tell your GP if someone has noticed loud snoring or gasping during your sleep. These can be signs of sleep apnoea, where breathing repeatedly stops and starts during sleep, leaving us tired during the day.5
Discuss tiredness before increasing the dose
If you’re still feeling tired before a planned dose increase, speak to your prescriber first. Foundayo doses can increase after at least 30 days, depending on how well treatment is working and any side effects.1
Tell them if you’re struggling to eat, drink, or manage daily activities. They can decide whether to increase the dose or keep it the same for longer.
Don’t change your dose or how often you take Foundayo without advice from your prescriber.
Get urgent help for severe symptoms
Seek immediate medical advice for severe, persistent stomach pain, particularly if it reaches the back. This can be a sign of pancreatitis, inflammation of the pancreas.1
Ask your GP for urgent advice or call NHS 111 for dark urine, passing less urine, or dizziness when standing that doesn’t go away. Get urgent advice if vomiting prevents you from keeping fluids down.6
Call 999 if someone is unresponsive, or has signs of dehydration with confusion, difficulty waking, or difficulty breathing.6
Take home message
Foundayo can cause tiredness due to reduced appetite, which can mean we don’t eat enough to support our body’s essential functions, while vomiting and diarrhoea can cause dehydration and limit the energy and nutrients available to the body.
We recommend eating three main meals a day, including protein-rich snacks if needed, and choosing easier-to-digest cooked foods to support adequate energy and protein intake.
Even when we’re eating enough and staying hydrated, Foundayo’s effects on the brain could still contribute to tiredness. Animal research suggests these effects may make us sleepier or reduce our motivation to be active, making everyday activities feel harder.3,4,8,9
Speak to your prescriber if tiredness is severe, continues, or affects everyday life, especially before increasing your dose. Other medicines or health conditions may also need checking.
Second Nature combines medication support with guidance from registered dietitians and nutritionists, including balanced meals, meal routines, and help managing reduced appetite.
A study of our programme alongside semaglutide, the drug in Wegovy, found an average weight loss of 19.1% at 12 months among members who were still subscribed.7
Of all members with recorded 12-month weights, 77.7% lost at least 10% of their starting weight.7
Second Nature's Mounjaro and Wegovy programmes
Second Nature provides Mounjaro or Wegovy as part of our Mounjaro and Wegovy weight-loss programmes.
Why choose Second Nature over other medication providers, assuming you're eligible?
Because peace of mind matters.
We've had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro and Wegovy) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We're here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK's most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
