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Medical Guidance

Before you use any of Practically Slim’s diet products in order to start on a Very Low Calorie Diet (VLCD), please make sure you read the following medical guidance information.

Medical supervision by your General Practitioner is very important before starting any diet, but is particularly important before you start a VLCD.

If you are currently on any medication prescribed by your GP this will need to be monitored or the dosage adjusted as you lose your weight. Your blood pressure may need monitoring whilst you are on a VLCD.

Please remember that we at Practically Slim are not trained medical professionals and we need you to ensure you obtain proper advice and guidance from your own GP before commencing a VLCD.


A very low-calorie diet (VLCD) is a special type of diet that replaces all of your meals with prepared formulas, often in the form of meal replacement packs. A VLCD may be used for a short time to promote quick weight loss among some people who are considered to be obese.

What are the possible Side Effects of a VLCD?

Very low calorie diets can have temporary side effects for some individuals; these are normal and will disappear when returning to conventional food. Most side effects are experienced in the first few days; carbohydrate and caffeine withdrawal can take place when starting a programme, usually causing headaches. Simple pain killers and drinking extra water will help. Some people experience feelings of nausea or an upset tummy. This could be due to the high concentration of vitamins and minerals contained in the replacement meals. Drinking water before, during and after eating can ease this.

  • You may get bad breath. The fat burning process (ketosis) causes a type of acetone to be released in the breath (which may result in a metallic taste in your mouth). This normally improves as the body settles down; drinking lots of water to dilute the acetones, regular brushing of teeth (and tongue) and using a mouth wash will also help. A spray breath freshener can be used.

  • Feeling cold is a natural side effect of being on a VLCD, as the metabolic rate slows and blood flow to extremities is decreased, meaning that hands and feet can feel colder than usual. This is a temporary side effect and wrapping up warmly, drinking warm water and being more active to encourage better circulation will all help with this.

  • Constipation seems to be the most common side effect of being on a VLCD. Often toilet habits change for a number of reasons: as you are eating a lot less food there is less to be excreted so you may not need to 'go' as often as usual. However if it is difficult to pass motions then you may be constipated, which could be because you have not drunk enough water regularly and have become dehydrated. Increasing your water intake can help.

  • Cramp may occur when on a VLCD, caused by fluid imbalances in the body's tissues. The remedy is to drink more water. Sometimes adding a few grains of salt to soups or in water at bedtime might help.

  • For those who use a VLCD over a period of time hair shedding can be a natural and temporary side effect. This is because a shortage of calories can cause the body to slow hair production /re-growth, this will return to normal following the reintroduction of conventional food.

  • A woman's hormone balance can alter when she loses weight. Although most are not aware of any changes, for a few, periods may change in flow, duration or frequency.

Health contraindications

Sometimes, certain people are not suited to a VLCD and to follow a Practically Slim VLCD plan you need to be able to answer NO to all of the following questions:

  • Are you lactose intolerant?
  • Do you have an allergy to milk?
  • Do you have an allergy to soya?
  • Have you suffered severe trauma in the last six weeks?
  • Have you undergone minor surgery in the last two weeks?
  • Have you undergone major surgery in the last twelve weeks?
  • Do you have Diabetes type 1?
  • If you have Diabetes type 2 do you require medication?
  • Do you have liver or kidney disease?
  • Do you suffer with any form of acute or chronic renal failure?
  • Do you suffer from Porphyria?
  • Do you suffer from any Psychotic illness?
  • Do you suffer with severe depression or bipolar disorder?
  • Do you have a serious heart condition, heart failure, arrythmia?
  • Have you had a heart attack or stroke within the last twelve weeks?
  • Do you have any serious illness?
  • Have you ever suffered with an eating disorder such as Anorexia or Bulimia Nervosa?
  • Do you have epilepsy, seizures, convulsions?
  • Are you pregnant, given birth in the last twelve weeks or breastfeeding?
  • Active Cancer?
  • Gout (you are only allowed to start on a calorie programme of 1300 calories +permission from your Doctor)
  • Are you taking anti obesity medication?
  • Are you under 16 or over 75?