Gastric Sleeve Diet – Weeks 1 and 2

Image of consultant bariatric surgeon, Mr Rishi Singhal

Medically reviewed by Prof Rishi Singhal MBBS, MRCS, FRCS, MD  
By Heather Fry BSC (Hons)

What to eat on weeks 1 and 2 of the gastric sleeve diet

Eating three small meals, using smaller plates, chewing thoroughly, focusing on nutritious foods, avoiding high-calorie drinks, and refraining from snacking. Exercise regularly, maintain a food diary, take daily vitamins, and practice environmental control to foster a supportive home environment that aids your weight loss journey.

Phase 1: Weeks 1 and 2

A liquid diet should be consumed for the first 2 weeks following your gastric sleeve operation. This is to allow time for your body to heal and recover. If you move onto foods too quickly it can put pressure on the staple lines which could cause them to rupture. This would mean stomach contents would leak into your abdomen which is very dangerous. Please note that post-operative advice does vary between surgeons– if you are unsure of what to do, please contact us.

What is a liquid?

A liquid is any fluid that will pass easily though a straw. However, please do not use a straw as this can cause discomfort from taking in too much air. There are many examples in this guide that are suitable for you in this phase.

How much should I drink each day?

You want to make sure you are meeting your fluid requirements. Fluid requirements vary from person to person so keep an eye out on the colour of your urine. It should be a light-yellow colour 4-5 hours after you have woken up.

On average though, a good fluid intake is 2 litres per day. This will include water, or any meal replacement shakes or soups. Aiming for this amount will help reduce the chance of constipation which is very common after surgery.

Will I be able to drink normally?

Drinking in the early stages following surgery will be very different to how it was before. You will need to take your time and drink slowly. It’s best to take frequent small sips throughout the day. A good habit to get into is waiting 20 to 40 seconds between sips. Getting used to this now will help when you start to reintroduce food.

The ideal serving size is about 200mls – don’t over-face yourself with anything bigger. It’s quite normal for this volume to take up to 30 minutes to drink when you’re drinking so slowly.

Don’t leave long gaps between having a drink – spread your intake out evenly during the day. It will reduce you feeling lightheaded or nauseous and keep your digestive system stimulated.

You might find you can drink a bit quicker than what we have described above and that’s OK. Everyone is different but the main thing is to avoid any discomfort or pain.

What can I drink?

Following surgery, you will be advised to follow a high protein diet. It’s likely you’ll need to aim for 70-80g of protein per day to ensure your body can heal well.

Focus on high protein liquids first. Some examples of high protein fluids are:

• 200ml cow’s milk (includes lacto-free milk) with 1 heaped tablespoon of skimmed milk powder (13g) added (11g protein).
• 200ml soya milk (6g protein).
• Meal replacement shakes e.g., Asda Great Shape, Celebrity Slim (vegan options available), Lighterlife Fast, SlimFast Advanced Vitality (vegan options available), SlimFast High Protein, Tesco Slim (protein content varies from 12g to 26g per shake).
• ½ can (200g) lentil/pea and ham/bean soups thinned with milk or stock and 1tbsp skimmed milk powder (9-11g protein).
• 200ml of any other flavour of soup (at the right consistency) with 2tbsp of skimmed milk powder added (>9g protein).
• Any protein shakes. There are many vegan options available if you find the milkbased ones cause any nausea or diarrhoea (protein content varies from 12g to 26g per shake).
• Smooth high protein yogurts thinned down with milk or water to a thin consistency (around 20g protein).
Other fluids you can drink freely are:
• Water
• Tea (including fruit and herbal)
• Coffee
• No added sugar squash
• No added sugar flavoured water
There are some drinks you might enjoy but limit to 1 or 2 per day as they can be high in salt or sugar but low in protein:
• Bovril/Marmite/Oxo
• Light hot chocolate (e.g., Cadbury Highlights, Options)
• Light malted drinks (e.g., Horlicks, Ovaltine)
• 100ml fruit smoothie or fresh fruit juice (diluted 50:50 with water)

Time Liquid Protein content (g)


200ml cow’s milk with 1 heaped tbsp of skimmed milk powder (13g). Warm up and add coffee if preferred.


200ml SlimFast Ready-To Drink shake


200ml cow’s milk with 1 heaped tbsp of skimmed milk powder (13g). Warm up and add coffee or light hot chocolate if preferred.


200ml (1/2 can) pea and ham soup, blended with 1tbsp of skimmed milk powder


Content100g high protein yogurt thinned with 100ml milk


200ml water/tea/squash/coffee


200ml (1/2 can) lentil soup, blended with 1tbsp of skimmed milk powder


200ml water/tea/squash/coffee


200ml cow’s milk with 1 heaped tbsp of skimmed milk powder (13g). Warm up and add light malted drink if preferred.

Do I need to avoid anything?

There are a few things you need to avoid during this phase to prevent any pain or problems:

• Sugary drinks such as flavoured water, squash, and still-ready mixed fruit drinks (e.g., Ribena, Oasis). Sugar-free or no added sugar options are fine.• Full sugar varieties of hot chocolate or malted drinks.
• Any carbonated drinks. These can cause extreme pain from the gas. It is advised to generally avoid them long-term.
• Alcohol. Your tolerance of alcohol following weight loss surgery is greatly reduced and can cause dehydration so best to avoid it in this phase.
• Milkshakes that aren’t a meal replacement shake e.g., Frijj, Galaxy, Mars, Shaken Udder, Yazoo. They tend to be very high in sugar.
• Tablets. Some medications may need to be crushed or taken in liquid form for the first 6 weeks after your surgery. It is best to check with your doctor before crushing your pills, as many medications are slow-release and cannot be crushed. Also, please check with your doctor before restarting medication for diabetes, as your requirements are likely to be much less than they were before your surgery.
• Medications that are irritating to the stomach, especially non-steroidal anti-inflammatory medicines such as aspirin, ibuprofen, diclofenac, sulindac, celecoxib, diflunisal and naproxen. If you are unsure, ask the Healthier Weight medical team for advice.

Ready to take the next step?

Image of consultant bariatric surgeon, Mr Rishi Singhal

All content on this page is reviewed by a multi-disciplinary team lead by Prof Rishi Singhal.

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