Obesity, Diet and Nutrition
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  • WHO estimates prevalence of obesity has tripled since 1970s
  • In 2016 – 2 billion adults worldwide were overweight or obese
    • In Australia, 2/3rds of adults are overweight or obese
  • Due to increase in availability of energy dense foods and decrease in activity
  • Also complex contributory genetic factors – not well understood
  • Resulted in increased prevalence of cardiovascular disease, diabetes and osteoarthritis
  • Weight loss is associated with:
    • Reduced BP
    • Reduced Cholesterol
    • Reduced incidence of osteoarthritis
      • For every 0.45 kg lost, there is a 1.8 kg reduction in knee joint stress
        • Approximately x4 reduction in joint stress for each kg of weight loss
      • Losing 10% of weight can negate the need for knee replacement
      • Patients who lose weight prior to knee replacement have reduced complications
    • Reduced overall mortality
    • Reduced chronic pain
    • Reduced risk of depression and anxiety
    • Reduced risk of sleep apnoea
    • Reduced risk of GORD and urinary incontinence
    • Reduced risk of many other diseases!
  • Abdominal obesity carries a higher risk – waist circumference is important!
  • Secondary / pathological causes are rare
  • Even small weight loss (e.g. 5% of body weight) is associated with reduced cardiovascular and diabetes risk
  • Weight loss is said to be 80% attributable to diet, 20% to exercise
    • It’s hard to out-exercise a bad diet”
    • Having said that, highly motivated patients, doing large amounts of exercise can probably attribute more than 20% of their weight loss to exercise


Complications of obesity


History taking for obesity

Ask specific questions. It’s not useful to ask “Do you have a good diet?” because almost everybody will answer “Yes!”

Be sensitive. Almost all patients will underestimate their food intake which may result in a denial of over-eating. Keeping a strict food (and mood) diary can help establish the baseline.


  • How many meals do you eat per day?
  • Who prepares your food?
  • Do you eat breakfast?
  • Do you know how many calories you are eating?
  • Are you eating fresh fruit and vegetables?
  • What proportion of your meals is made up of fat / carbohydrates / protein?
  • How much sugar do you have (including sugary foods and drinks – e.g. fruit juices, fizzy drinks)
  • What snacks do you eat?
  • Calories from drinks (tea / coffee – especially if milky, fruit juices, alcohol)
  • Do you smoke?
    • Smoking cessation is associated with, on average – 9Kgs of weight gain!
  • Ask about previous diets / previous efforts at weight loss
  • Ask about medications. There are many medications (particularly ones for psychiatric conditions) associated with weight gain. Common examples include:
    • Anti-epileptics – sodium valproate and carbamazepine
    • Contraceptives – Depot progesterone
    • Corticosteroids
    • Antihistamines
    • SSRIs
    • Anti-psychotics – particularly clozapine and olanzapine
    • Lithium
    • Anti-diabetic agents – sulphonylureas, glitazones, insulin
  • Ask about common conditions that can cause weight gain:
    • Hypothyroidism – any FHx? Any other symptoms suggestive of hypothyroidism?
    • PCOS – poly-cystic ovary syndrome – ask about other symptoms – acne, male pattern hair growth, irregular periods.
    • Poor sleep
    • Stress / mental health disorders
    • Sleep apnoea
    • Anything that causes reduced mobility

I often ask patients to take me through their typical day. “Tell me everything you eat and drink from the moment you get up until you go to bed. Let’s start with breakfast….” Don’t forget to specifically ask about snacks between meals, and liquid calories.

Even with patients who think they have an excellent diet, I am almost always able to find some areas for improvement, and I have found this approach is much less confrontational. Often just by going through this process, patients pickup on several things themselves. – Dr Tom Leach



  • Ask about types of physical activity and how strenuous
  • Most guidelines recommend at least 30 minutes on 5 days per week of “moderate intensity” physical activity
    • Some define “moderate intensity” as something that gets your heart rate to about 120 bpm, or the point at which you are breathing more quickly, but still able to speak in full sentences
    • This should include muscle strengthening activities twice per week
    • Avoid prolonged periods of sitting
  • Consider offering patients a “written prescription” for exercise – g. a realistic written exercise plan – individualised for your patient
  • Regular exercise is associated with reduced cardiovascular disease risk benefits regardless of weight loss– i.e. regular exercise without weight loss still has benefits
    • The cardiovascular benefits of exercise plateau at around the recommended level of exercise (30min / 5x per week)
    • Any additional exercise beyond this will improve fitness but is not strongly correlated to decrease in cardiovascular risk
    • Weight maintenance is also an admirable goal – given that most adults gain weight over time (between 1.5 and 3.5kg every 10 years on average)


  • There is an association between obesity and poor sleep
  • Ask about sleep apnoea
  • Provide advice on sleep hygiene
    • Aim for 7-8 hours to sleep per night
    • Regular bed time
    • Regular pre-bed time routine – ideally avoiding screens in the last hour before bed
  • Eating the evening meal earlier (before 7pm) may be beneficial
    • There is some emerging evidence that periods of “fasting” between meals may affect metabolism – aiming for 3 meals a day, with 6 hours between them and a 12 hour “fast” overnight may be beneficial


  • Ask about mental health, and eating as an emotion response
  • Ask about compulsive eating


Be sensitive. Many patients are highly conscious of their weight. A thorough examination should include:

  • Weight
  • Height
  • BMI
    • Normal – 20 -25
    • Overweight – 25-30
    • Obese – 30+
  • BMI in children
    • >85th Percentile for weight – overweight
    • >95th percentile for weight – obese
    • Be aware of possible genetic causes in children (rare), e.g. Prada-Wili Syndrome
  • Blood pressure
    • Undersized cuff (e.g. regular cuff on a large arm) can overestimate BP
  • Waist circumference
    • Better predictor of cardiovascular disease and diabetes than weight alone.
    • >94cm in men and >80cm in women is clinically significant
    • Consider the waist to hip ratio
      • >1.0 significant in men
      • >0.9 in women
    • Urine Dip
      • For glucose (diabetes)
      • For renal disease (protein)



Investigations are not always indicated.

  • Only about 1% of cases of obesity are the result of an underlying endocrine disorder. 

If there is clinical concern, consider testing for the following:

  • Thyroid Function
    • TSH – if not in normal range, perform fT4
  • PCOS
    • Diagnosis requires 2 of the below (and thus can be clinical – without the need for investigations):
      • Signs of hisutism
      • Oligomenorrhoea (<9 periods per year)
      • >12 peripheral ovarian follicles OR ovarian volume >10mls on USS
  • Cushing’s Syndrome

An initial work-up might involve screening for conditions associated with obesity, such as:

  • Hypercholesterolaemia (check fasting cholesterol including LDL and HDL)
  • Diabetes – Fasting blood sugar / HbA1c
  • Liver Function Tests
  • Urea and Electrolytes
  • Sleep study – if concern for sleep apnoea
  • ECG



The 5A’s Approach

  • Ask – about their concerns about their weight. Ask if they have tried to lose weight
  • Assess – BMI, waist circumference, diet, physical activity, motivation, health literacy
  • Advise – weight loss and describe the benefits. Aim for an increase of physical activity – up to 60 minutes per day of moderate intensity – 5 days per week
  • Assist / Agree – set achievable realistic goals (see goal setting below). Referral to allied health professionals (Dietician, exercise physiologist).
  • Arrange – Follow – up – at least every 2-3 months. Monitor for relapse. Come up with a maintenance program. Consider referrals as required and consider option of bariatric surgery.


Basic Principles of Management

  • Reduce energy intake
  • Change diet composition
  • Increase physical activity
  • Behavioural change

Aim for 5-10% weight loss.

Aim to make long-term sustainable changes that should last > 1 year. You can ask your patient if they think they will be able to sustain this for a year.

Aim for a calorie deficit of 600 calories per day and a steady weight loss. Weight loss of 1kg per week is considered sustainable, but more slowly (e.g. 1kg per month) may be more appropriate.

Try to assist the patient in coming up with a diet and exercise plan. Set achievable goals. Be specific – and often small modest changes – for example – only have take-away one night per week. Make a meals list and a shopping list at the start of each week. Cook some meals in advance at home for nights when you don’t feel like preparing a meal.

It may be useful to keep a food diary of everything the patient eats and drinks for one week. This can give an understanding of how many calories they are eating and where they are coming from, and can help the doctor and dietician come up with suitable alterations.


Goal setting

Using the SMART system can assist with goal setting:

S – Specific

M – Measurable

A – Achievable

R – Realistic

T – Time frame

Goals can also be described as process goals or outcome goals. Often an outcome goal requires a number of process goals for it to be achieved.

For example:

  • “I will try to lose weight” is not a useful goal
  • “I will walk to school three times a week” is a useful process goal
    • Typically multiple process goals will need to be combined to reach an outcome goal
  • “I will lose 3kgs in the next 6 weeks” is a useful outcome goal



  • Dietitian
  • Exercise physiologist


Specific Diet Advice

  • Avoid processed foods
  • Avoid added sugar and salt
  • Two servings of fruit per day
  • Five servings of vegetables per day
  • Avoid sugary drinks
  • Limit red meat to 3-4 servings per week
  • Encourage a good breakfast
    • Eating breakfast (as opposed to not eating breakfast) is associated with a lower risk of obesity and better weight management


VLED – Very Low Energy Diet

VLEDs involve the use of meal replacements (e.g. SlimFast or other similar meal replacement shakes) to provide a set number of calories, with the aim of providing only a small number of calories per day (usually 500 – 800)

  • Should only be done with medical supervision – follow-up every 1-2 weeks initially
  • Indicated in patients with a BMI >30 or BMI >27 with co-morbidities
  • Patients eventually weaned off VLEDs onto a nutritionally complete diet with strict portion control

Side effects of VLED

  • Increased risk of gallstones
  • Increased sensitivity to cold
  • Fatigue
  • Dairrhoea / constipation
  • Bad breath
  • Muscle cramps
  • Irritability
  • Menstrual cycle disturbances

A typical regimen might include x2 meal replacement shakes, with a single “normal” meal, involve a healthy balance of foods.

This is often done in combination with medical therapy


Several medications are available to assist weight loss.

None of them are hugely effective, and all carry risks and side effects. They can be a helpful tool for some patients, but it is important to explain the expected outcomes.

There is no good evidence for other dietary or nutritional supplements.

Medication should generally be considered after diet and lifestyle changes have been tried, and:

  • BMI >30, OR
  • BMI >27 with obesity-related complications (e.g. T2DM, renal disease)

Medications available to assist with weight loss include:


  • The first approved medication for weight loss
  • Given orally
  • Can be taken long term
    • Reassess effectiveness of treatment every 12 weeks and cease if no longer effective
  • Reduces the absorption of fat by inhibiting pancreatic an gastric lipases
  • Often causes diarrhoea and GI upset
    • Steatorrhoea
    • Fatty Faecal Incontinence
    • Frequency and Urgency
    • Symptoms tend to be correlated to the level of fat intake
    • Advise <30% of calories as fat to minimise this risk
  • Reduces the absorption of fat soluble vitamins (A, D, E, K) – but not thought to be clinically significant. Consider supplementation in patients taking orlistat
  • Associated with modest weight loss of 2.6 – 3.7 Kg when taken for a year
    • The problem is many patients cannot tolerate the side effects and thus do not use it long term!
  • Proven to reduce the risk of developing T2DM over a 4 year period when given to those with impaired glucose tolerance
  • Recommended for patients with a BMI >30, or a BMI >27 with comorbidities
  • Contraindicated in:
    • Breastfeeding women
    • Adults with malabsorption



  • Commonly known as Duromine and Metermine (brand names)
  • Thought to suppress hunger
  • Maximum duration – 12 weeks
    • Then, drug-free period of 4-12 weeks, before starting another course
  • A type of amphetamine – has the potential for abuse
  • Is expensive
  • Long-term safety unknown
  • Associated with wide range of side effects:
  • Risk of tolerance
  • Typically recommended only for those with BMI >30, as the increased cardiovascular risks are thought to outweigh the benefits in those with a lower BMI


Liraglutide (Saxenda(R))

  • Analogue of glucagon-like peptide-1 (GLP1 receptor agonist)
  • Used mainly in diabetes, also prescribed for weight loss
    • Again, only recommended if BMI >30 or BMI >27 and a weight-related co-morbidity
  • Increases glucose-dependent insulin secretion
  • Delays gastric emptying and reduces hunger
  • Requires daily sub-cutaneous injections
  • In trials – at one year – patients had lost 4-5% more of their body weight than those on placebo
    • 2/3rds of patients had lost >5% body weight
    • 1/3rdhad lost >10%
    • Weight loss plateau at about 9 months
    • Weight was regained when treatment stopped
    • Weight loss was dose dependent
  • Beware of the contrainidcations
    • FHx or PMHx of medullary thyroid carcinoma
    • Multiple endocrine neoplasia 2
    • Pregnant or breast feeding
    • PMHx of pancreatitis
    • On insulin or other GLP-1 agonists
  • Side effects include:
    • Nausea / vomiting – in up to 50% of patients. Tends to improve with continuing treatment
    • Other abdominal symptoms – diarrhoea, constipation, pain, GORD
    • Associated with pancreatitis and gallstone formation
    • Thyroid tumours
  • Dose
    • Start at 0.6mg once daily
    • Increase weekly bu 0.6mg to a maximum of 3mg once daily

 Bupropion / naltrexone combination (Contrave(R))

  • Approved for use in Australia in 2019
  • May not be available in the UK
  • Bupropion is a dopamine and noradrenaline re-uptake inhibitor
  • Naltrexone is opioid antagonist – also used to assist with alcohol addiction
  • Studies show an average of 4.8% weight loss when used for a year
  • Maybe particularly useful in patients who struggle with food cravings and modifying their food intake
  • Side effects:
    • Nausea
    • Vomiting
    • Headaches
    • Dizziness
    • Dry mouth

Endoscopic Management Therapies

An alternative to bariatric surgery. There are two main types:

Intragastric Balloon

  • A balloon is placed in the stomach endoscopically. It is then filled with saline and methylene blue (this helps patients identify a leak)
  • The physical mass of the balloon provides a feeling of satiety. It also helps to delay gastric emptying
  • Associated with a reduction of BMI of around 6 at twelve months

Endoscopic Sleeve Gastroplasty

  • Essentially part of the walls of the stomach are sewn together to reduce gastric volume
  • Very new treatment – long term data not yet available
  • Assocaited with BMI reduction of 5-8 (or 15-20% of total body weight) at two years post procedure, in patients with a starting BMI of 30-40

Bariatric Surgery

Used as a last resort. Aims of surgery are to reduce food intake by restricting gastric capacity.

Surgical treatments have been shown to be more effective than non-surgical treatments. In patients with a BMI >35, surgery typically results in 20-30% weight loss. There is good evidence at 10 year follow-up that the weight loss associated with bariatric surgery has sustained health benefits.

Surgery is recommended for adults with BMI >40, or >35 with comorbidities, or BMI >30 with T2DM and increased cardiovascular risk (do cardiovascular risk score).

There are several different types of procedure with differing outcomes. Common examples include:

Laparoscopic adjustable gastric banding (LAGB)

  • Band is placed around the stomach at the proximal end, creating a small pouch at the top of the stomach.
  • Band can be adjusted over time to alter the amount of restriction
  • Adjustments made by injecting or withdrawing fluid from a subcutaneous access port
  • Safest and least invasive type of bariatric surgery
  • Weight loss peaks at about 18 months post-procedure
  • Can make some foods difficult to tolerate

Sleeve Gastrectomy

  • Part of the fundus and body of the stomach are removed – about 75% of the stomach in total
  • Stomach volume typically reduced from 2500ml to 200ml
  • Permanent fixed reduction
  • Patients require mulitvitamin, and sometimes iron and B12 supplementation for life

Roux-en-Y gastric bypass (RYGB)

  • Small stomach pouch created, and the lower stomach, duodenum and first portion of the jejunum are bypassed.
  • Smaller stomach restricts intake
  • Bypass of first portion of small intestine reduces absorption of nutrients (and therefore calories intake)
  • Multivitamin supplementation required for life

Biliopancreatic diversion

  • Similar to a Roux-en-Y bypass
  • Lower portion of stomach removed and duodenum and first part of jejunum are bypassed


  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy
  • Pharmacotherapy for Obesity – RACGP

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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