Obesity (ILO/IMO Guidelines Appendix E E65-68. Appendix C also relevant)

Impairment and risks

Obesity is a common cause of physical incapacity in serving seafarers. Other causes of physical incapacity include musculoskeletal disease and injury and limitations to heart and lung function, especially during exercise. All these causes can interact as obesity raises the demands on the heart and lungs during exercise and also increases the risk of future musculoskeletal damage and heart disease.


Immediate risks from obesity include:

  • Inability to undertake arduous emergency tasks such as fire-fighting, evacuation from the vessel and recovering people from the water. Difficulty entering and leaving restricted spaces, during normal duties and especially if needing rescue because of collapse or injury
  • Increased risk of injury from falls and of acute illness and incapacity while at sea
  • Inability to fit into protective clothing and life saving equipment.
  • Exceeding the design standards for equipment used to work at heights and for use in life threatening situations, for instance emergency chutes and free fall lifeboats.

These limitations create risk both for the seafarer themselves and for other crew members.


In the longer term obesity is a risk factor several medical conditions that affect fitness:

  • ischaemic heart and other vascular disease,
  • hypertension,
  • type 2 diabetes,
  • sleep apnoea
  • musculoskeletal damage, especially in weight bearing parts of the body such as the hips, knees and lower back.

All of these longer term risks have the potential to lead to medical emergencies at sea or early termination of work because of the development of disqualifying conditions or other failures to meet medical standards designed to protect safety and reduce the probability of illness at sea.


Rationale and justification

There are two aspects to be considered:
- Relationship between obesity and current capabilities. There are few studies on seafarers. Most available evidence from studies in other settings points to a progressive reduction in physical work capacity and in mobility with increases in obesity but with very large variations between individuals. There is evidence of an increased rate of industrial accidents with increasing obesity.
- Obesity as a risk factor for other conditions. Most of the large population studies on heart disease, diabetes and overall mortality show an increased frequency of adverse outcomes with increasing weight. The probability of arthritis of the hip and knee requiring surgical treatment increases with excess weight.

There are a number of measures of obesity that are used:

  • Body Mass Index (BMI) is the product of weight in kilogrammes / height in metres x height in metres. It is a simple figure to derive from data commonly collected at medical examinations but can be affected by the shape of the body frame and its muscle mass. It is not the best predictor of long-term risk from obesity associated conditions.
  • Central adiposity – fat in and around the abdomen is a better predictor of future risk from obesity associated conditions. It is most conveniently assessed by measurement of waist girth in a specified way. Increased girth shows a good relationship with increased long term disease risk, irrespective of other facets of body size.
  • Skinfold thickness
  • Total body fat by body impedance measurement.


For many of the short-term risks from obesity measurement of capability is required. (See ILO/IMO guidelines Appendix C)

Targets based on reductions in measured obesity or on improved performance at capability tests are effective motivational tools to use to secure weight reductions and fitness improvements.


Clinical assessment and decision taking

a) Approaches to decision taking on obesity

Obesity that interferes with the safe performance of normal or emergency duties or that carries a risk of incapacitation while working at sea prior to the next medical which is such that it is considered unacceptable in terms of the individual or the safe and efficient operation of the vessel is a valid reason for making a seafarer unfit or for restricting their duties.
In general long term health risk management in seafarers as in other members of the working population is seen as largely a matter of personal commitment and choice, backed by enabling measures like smoking bans or food labelling. Even for raised blood pressure the level at which a prohibition on work at sea is set is well in excess of the level of control needed to prevent longer-term vascular damage. Hence action to reduce the long-term risks from obesity will largely be a matter of health promotion and education, with reminders of the risk of reduced physical ability and restriction of duties because of this.
While the assessment of risk of incapacitation from a complication of obesity is an actuarial judgement based medical evidence from similar cases, the assessment in a clinical setting of current capability to perform shipboard duties is not, except in very general terms, possible.

In practice the following options for obesity assessment may be considered as ways to supplement the physical capability requirements criteria in the ILO/IMO Guidelines:

  1. A fixed limit using a measure such as a BMI of 35 or 40. Unfit if exceeded.
  2. BMI of 30 or 35 as an initial screen with a requirement to pass either a standardised exercise test, have an assessment of physical ability or demonstrate the ability to perform normal and emergency duties if above this level. An acceptable standard in one or more of these assessments could be required.
  3. In addition or instead of this approach a level of BMI above which person is considered fit only if no other form of ill health that might limit physical capabilities (e.g. musculo skeletal disease) or increase risk of future incident (e.g. diabetes) is present.
  4. No use of weight measurement but application of capability tests to all seafarers on a regular basis, or when there are doubts about performance.


Because weight gain is progressive and can be controlled by the individual in most cases given suitable dietary choices, an approach which aims to halt weight gain before it reaches a level where it can cause risks and which encourages weight loss is needed. This can be re-enforced with the prospect of limitations to employment, if weight has reached a level where unacceptable levels of risk are imminent.

Demonstrating that the seafarer cannot meet the requirements of their job or showing them that their ability to exercise is impaired can be far better means of persuasion than weight measurements, as they can be directly related to their ability to work at sea.

Where there is continuity of employment and of medical examination encouragement and sanctions can be incremental.

  • Advice on diet and weight reduction, with targets set. This can be backed by wider screening for risk factors, especially for ischaemic vascular disease and diabetes.
  • Issue of short term certificate of fitness or one limited to certain waters or duties, with re-issue or removal of restrictions dependent on a realistic level of weight loss and/or improvement in physical ability
  • Temporary unfitness, with re-issue dependent on a realistic level of weight loss and/or improvement in physical ability. Referral to dietician or for other weight loss programme.
  • Permanent unfitness. This needs to be supported by confirmation that the problem is long-term and not amenable to improved control as well by evidence of the individual's inability to perform duties in a safe and efficient way.
  • Where compliance is achieved by this approach it will usually be at a stage when some weight loss, or physical improvement has been achieved but more is required. Hence continuing surveillance by the same clinical team is needed to ensure that the seafarer and the assessors are all working towards the same targets.
  • The nature and quality of food available at sea is a major contributor to effective weight control and individual approaches may need to be supplemented by recommendations to shipping managers of food purchase and training for ships cooks on the preparation and serving of sustaining low calorie and low fat foods.


Some of the larger maritime employers with employees on permanent contracts have corporate obesity programmes. These are linked to dietary provisions and exercise facilities on board their vessels. In a few cases these programmes include regular physical ability testing for all employees as a condition of continuing employment. This is aimed at the recruitment and retention of a fitness oriented workforce and this is seen as having both direct health benefits and indirect ones concerned with commitment and morale.

Under conditions of casual employment on single voyage contracts, and where a different doctor may undertake each medical, continuity is difficult. The decision taken by the examining doctor has to reflect the forms of assessment that are practicable in a clinical setting. In cases of doubt about fitness or motivation to control weight it is reasonable to issue a certificate where fitness is conditional on the employer confirming that the seafarer can meet the physical demands of their routine and emergency duties or on the provision of suitable dietary choices.


b) Suggested framework for assessment

Decision tree for chapter 13. Obesity

Click "START" to begin the decision tree