What goes into food?

In order to lose weight and remain healthy you need to eat well. Having knowledge of the basics helps when selecting what you are going to eat. Try not to make things too complex, and always aim to keep as many fresh foods in your diet as possible.


About 50 per cent of the food we consume is made up of liquid. We need a minimum of one litre of water every day, but a lot of this will come from our food. People who are losing weight, people who have problems with constipation and those who are exercising will need to drink more. You need to avoid sweet and milky fluids. Most people who drink these things are not really thirsty – they are just filling in time.


Most of the protein we eat we get from meats, fish, eggs and dairy products. We absorb plant protein less efficiently than we absorb animal protein, and many supposedly high – protein plant foods contain less protein than we think. We need a minimum of 25 grams of protein per day, but its better to aim for a minimum of 30 – 40 grams. The following calories and protein are provided by 100 grams of these foods:

  • Eggs: 150 calories; 13 grams protein
  • Chicken: 220 calories; 25 grams protein
  • Beef: 330 calories; 14 grams protein
  • Fish: 90 calories; 19 grams protein
  • Canned tuna in water: 110 calories; 25 grams protein
  • Cheese: 400 calories; 25 grams protein
  • Sugar: 390 calories; no protein
  • Cottage cheese: 100 calories; 11 grams protein
  • Yoghurt (Greek): 60 calories per 100 ml; 10 grams protein
  • Tofu: 75 calories; 8 grams protein
  • Baked beans: 150 calories; 6 grams protein
  • Bread: 290 calories (two – and – a – half slices of toast); 12 grams protein


Deficiency in fibre is very common in patients after weight loss surgery. Unless you can get your bowels moving at least every two day s you will develop debilitating and permanent constipation. Good sources of fibre include fresh fruits, vegetables and salads. Breakfast cereals with bran can be high in fibre. I recommend unprocessed bran (with breakfast cereal), or using supplements containing soluble fibre (Benefibre) or psyllium (which creates less gas) that you can put into water, such as Metamucil


Carbohydrates are crucial for our day – to – day functioning, but they are the food group most commonly associated with the development of obesity and the recurrence of obesity after weight loss. Carbohydrates are the key ingredient in breads, snacks, potatoes, fruit juice, alcohol and sweets. Eating carbohydrates promotes hunger, which promotes more carbohydrate eating. ‘Low – carb ’ versions of these foods are still just carbs.

Our minimum requirement is about 50 grams of carbohydrate per day; most people should try to limit their intake to 60 – 100 grams per day, unless they are doing a lot of exercise. Carbohydrates are converted into sugar, and eating sugar makes us produce the hormone insulin. The combination of insulin and sugar creates obesity. Anyone wanting to lose weight needs to switch his or her body from using sugar as a fuel to using fat. Burning fat is called ketosis. (W hen you burn fat you turn it into ketones which is an energy source your body can use instead of sugar.) It takes many hours to ‘turn on’ ketosis, but a small carbohydrate snack will turn it off. Anyone who wishes to lose weight will only do so if they limit their carbohydrate intake and start using stored fat for energy


We get calcium from dairy products, meat and fish. While we recommend that weight loss surgical patients eat foods that are high in calcium (except cheese), there is no evidence t hat any form of dietary supplementation of calcium makes any difference to bone strength. Patients with weak bones, a significant family history of weak bones, or who do not exercise should probably take a calcium tablet daily. It may be safer and more cos t effective for patients to have a bone density scan every three years after surgery.

Vitamin D

We create vitamin D in our own bodies when we are exposed to sunlight. It also exists in small amounts in many foods. Vitamin D helps us use calcium effectively to maintain bone strength, and has a role in immunity. It is probably more important than dietary calcium. Vitamin D deficiency is Australia’s most common vitamin deficiency. While many people can have low vitamin D levels without harm, it is likely to be a very important vitamin in patients losing weight. Daily supplements, monthly tablets and injections are available. The stronger tablets are probably more effective but overdosing isn’t advised.


Folate is a vitamin found in fresh fruit, vegetable s and salad. Patients who don’t get enough folate usually look and feel sickly. A daily multivitamin will provide sufficient folate for patients after surgery.


While present in many foods and all multivitamins, thiamine is a very important vitamin. Post – operative patients who experience vomiting and don’t take a multivitamin to supplement their thiamine levels are at very high risk of developing irreversible neurological injury and dementia

Vitamin B12

Vitamin B12 is the second most frequently deficient vitamin in Australia. It is only found in animal protein. If someone is developing a deficiency in B12, the only effective way to supplement it is via injections from your GP (every three to six months). All gastric bypass patients, many sleeve gastrectomy patients, and some lap band patients need these injections.


We get iron from meat proteins. There are small amounts in vegetable protein. Iron deficiency is quite common, and it is significant for two reasons:

  • Iron deficiency can lead to a drop in blood production, which will lead to fatigue and reduced exercise capacity
  • Iron deficiency is the first sign of many bowel and stomach cancer

Patients having gastric bypass often need iron supplements. Patients with other operations sometimes need iron supplements. Patients with unexplained iron deficiency need to be investigated in order to rule out cancer.

Other minerals : iodine, zinc, selenium, copper

In Australia our soils are deficient in iodine, so a multivitamin with iodine is advised. These other minerals are also important, and a daily multivitamin will be sufficient for most patients. Patients who have diarrhoea, vomiting, poor diet or are considering pregnancy should probably take a multivitamin twice daily. Zinc, iron and silica may help reduce the risk of early hair loss after surgery.

Vitamin and mineral deficiencies

I have seen patients with a number of unpleasant vitamin and other deficiencies after weight loss surgery. They are all a result of the combination of vomiting plus poor – quality diet plus not taking vitamins. Sometimes the illnesses from these deficiencies can be irreversible. A multivitamin a day forever is the minimum requirement for all weight loss surgery patients. Blood tests should be done at least every year for iron, vitamin B12, folate, calcium and vitamin D. Blood count and liver and kidney function should be tested at the same time.

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