Weight Gain

By far the commonest cause of this problem is simple obesity. This is 50% commoner in women, who also present more often than men. It may be the primary problem presented or it may be a ‘while I’m here’ symptom – either way, it tends to be viewed as a ‘heartsink’ symptom, as such patients may have unrealistic expectations of what the doctor can achieve.

Published: 2nd August 2022 | Updated: 15th August 2022

Differential diagnosis

Common Diagnoses

  • Simple Obesity (Usually Hereditary Component with Poor Diet and Lack of Exercise) Hypothyroidism
  • Pregnancy
  • Oedema of any Cause (e.g. Cardiac Failure, Renal Failure, Hepatic Failure)
  • Alcohol Excess

Occasional Diagnoses

  • Menopause
  • Iatrogenic (e.g. Steroids, Insulin, Sulphonylureas, Oestrogen, Pizotifen)
  • Polycystic Ovary Syndrome
  • Large Single Ovarian Cyst
  • Physical or Mental Disability Restricting Activity (e.g. CVA, Down’s Syndrome)

Rare Diagnoses

  • Anabolic Steroid Abuse
  • Cushing’s Syndrome
  • Hypothalamic Lesion or Hypopituitarism
  • Insulinoma
  • Rare Genetic Syndromes Such as Prader–Willi Syndrome

Ready reckoner

Key distinguishing features of the most common diagnoses

Simple ObesityHypothyroidismPregnancyOedemaAlcohol
Pitting OedemaPossibleNoPossibleYesPossible
Only Abdominal Girth IncreasedNoNoYesNoPossible
Long HistoryYesPossibleNoPossiblePossible
Palpable LiverNoNoNoPossiblePossible
Otherwise WellYesPossiblePossibleNoNo

Possible investigations

Likely: TFT.

Possible: Urinalysis, FBC, LFT, U&E, pregnancy test, total testosterone, SHBG, cardiac investigations if the cause is possible cardiac failure, pelvic ultrasound.

Small Print: Secondary care investigations for endocrine dysfunction.

  • Urinalysis: Proteinuria may be present in oedema caused by underlying renal disease.
  • FBC: Anaemia may precipitate cardiac failure; MCV raised in hypothyroidism and alcohol excess.
  • TFT: Will reveal hypothyroidism.
  • U&E: Deranged in renal failure and Cushing’s syndrome.
  • LFT: To check for liver failure, evidence of alcohol abuse and hypoproteinaemic states.
  • Total testosterone normal or moderately elevated, and SHBG normal or low in PCOS.
  • Pregnancy test: To exclude pregnancy if this is a possibility.
  • Pelvic ultrasound: Will confirm ascites, ovarian cysts and pregnancy.
  • Cardiac investigations: CXR, ECG, BNP and echocardiography if the underlying cause is possible cardiac failure.
  • Secondary care investigations for endocrine dysfunction: For insulinoma, hypopituitarism, Cushing’s syndrome.

Top Tips

  • Patients presenting with weight gain, especially if it is a long-term or fluctuating problem, usually have a clear agenda of their own – such as wanting a blood test or drug treatment. Much time can be wasted giving unwanted advice about diet and exercise which the patient will have heard before. Establish the patient’s agenda early in the consultation.
  • Parents anxious about weight gain in their children often want to be reassured that the child’s ‘glands’ are normal. If the child’s height is in proportion to its weight, or the parents have a similar physiognomy, and the child is otherwise well, it is highly unlikely that there is an underlying cause.
  • Patients with Down’s syndrome have a relatively high prevalence of hypothyroidism – consider this possibility if a patient with Down’s syndrome experiences inexplicable weight gain.
  • Investigation is usually clinically unnecessary, but may be useful to clear the way to dealing with the real cause.
  • Correction of hypothyroidism may not solve a weight gain problem, merely unmask an underlying simple obesity. Don’t falsely raise expectations.

Red Flags

  • Establish whether the weight gain is diffuse or whether there is predominantly abdominal swelling. The latter may indicate pregnancy, ascites or a large ovarian cyst.
  • Recent onset of weight gain in an elderly patient suggests probable congestive cardiac failure or possible hypothyroidism.
  • Young women may not consider, or accept, a diagnosis of pregnancy as a cause of their weight gain. Arrange a pregnancy test if in any doubt.
  • The yield from routine blood tests is low – but consider investigation if the patient is unwell or the history atypical.
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Website disclaimer

Pulse Reference is based on the best-selling book Symptom Sorter.

The experts behind Pulse Reference are Dr Keith Hopcroft who is the co-author of Symptom Sorter, a GP in Essex and Pulse’s editorial advisor and Dr Poppy Freeman, a GP in Camden and also a clinical advisor to Pulse.

This website is for clinical guidance only and cannot give definitive diagnostic information. Practitioners should work within the limits of their individual professional practice, seek guidance when necessary and refer appropriately.