Workplace wellness programmes which aim to help employees stay fit, healthy, and - crucially - productive, do not reduce sick days, staff turnover or improve job performance, a major trial has found.

For the first time researchers, led by Harvard Medical School, have conducted a comprehensive trial to test the effects of diet advice, fitness coaching and mental health schemes offered by many businesses

While it found that employers with a wellness programme had more employees taking part in regular exercise and actively managing their weight, evidence of benefits in the areas which matter most to employers, and their profit margins, was scarce.

“Our findings show that health behaviours can respond to a workplace wellness program, but they also temper expectations of realising large returns on investment in the short term,” said Dr Zirui Song, lead author of the study published in the Journal of the American Medical Association.

Wellness schemes have boomed in recent years, stimulated in part by tech companies like Facebook which see gym memberships, catering and entertainment perks as a way of retaining top talent.

The worst jobs for your health Show all 10 1 /10 The worst jobs for your health The worst jobs for your health 10. Surgical and medical assistants, technologists, and technicians Overall unhealthiness score: 57.3 What they do: Assist in operations, under the supervision of surgeons, registered nurses, or other surgical personnel and perform medical laboratory tests. Top three health risks: 1. Exposure to disease and infections: 88 2. Exposure to contaminants: 80 3. Exposure to hazardous conditions: 69 The worst jobs for your health 9. Stationary engineers and boiler operators Overall unhealthiness score: 57.7 What they do: Operate or maintain stationary engines, boilers, or other mechanical equipment to provide utilities for buildings or industrial processes. Top three health risks: 1. Exposure to contaminants: 99 2. Exposure to hazardous conditions: 89 3. Exposure to minor burns, cuts, bites, or stings: 84 The worst jobs for your health 8. Water and wastewater treatment plant and system operators Overall unhealthiness score: 58.2 What they do: Operate or control an entire process or system of machines, often through the use of control boards, to transfer or treat water or wastewater. Top three health risks: 1. Exposure to contaminants: 97 2. Exposure to hazardous conditions: 80 3. Exposure to minor burns, cuts, bites, or stings: 74 The worst jobs for your health 7. Histotechnologists and histologic technicians Overall unhealthiness score: 59.0 What they do: Prepare histologic slides from tissue sections for microscopic examination and diagnosis by pathologists. Top three health risks: 1. Exposure to hazardous conditions: 88 2. Exposure to contaminants: 76 3. Exposure to disease and infections: 75 The worst jobs for your health 6. Immigration and customs inspectors Overall unhealthiness score: 59.3 What they do: Investigate and inspect people, common carriers, goods, and merchandise, arriving in or departing from the US or between states to detect violations of immigration and customs laws and regulations. Top three health risks: 1. Exposure to contaminants: 78 2. Exposure to disease and infections: 63 3. Exposure to radiation: 62 The worst jobs for your health 5. Podiatrists Overall unhealthiness score: 60.2 What they do: Diagnose and treat diseases and deformities of the human foot. Top three health risks: 1. Exposure to disease and infections: 87 2. Exposure to radiation: 69 3. Exposure to contaminants: 67 The worst jobs for your health 4. Veterinarians, veterinary assistants, and laboratory animal caretakers and veterinary technologists and technicians What they do: Diagnose, treat, or research diseases and injuries of animals and perform medical tests in a laboratory environment for use in the treatment and diagnosis of diseases in animals. Top three health risks: 1. Exposure to disease and infections: 81 2. Exposure to minor burns, cuts, bites, or stings: 75 3. Exposure to contaminants: 74 The worst jobs for your health 3. Anesthesiologists, nurse anesthetists, and anesthesiologist assistants Overall unhealthiness score: 62.3 What they do: Administer anesthetics or sedatives during medical procedures, and help patients in recovering from anesthesia. Top three health risks: 1. Exposure to disease and infections: 94 2. Exposure to contaminants: 80 3. Exposure to radiation: 74 The worst jobs for your health 2. Flight attendants What they do: Provide personal services to ensure the safety, security, and comfort of airline passengers during flight. Greet passengers, verify tickets, explain use of safety equipment, and serve food or beverages. Top three health risks: 1. Exposure to contaminants: 88 2. Exposure to disease and infections: 77 3. Exposure to minor burns, cuts, bites, or stings: 69 The worst jobs for your health 1. Dentists, dental surgeons, and dental assistants Overall unhealthiness score: 65.4 What they do: Examine, diagnose, and treat diseases, injuries, and malformations of teeth and gums. May treat diseases of nerve, pulp, and other dental tissues affecting oral hygiene and retention of teeth. May fit dental appliances or provide preventive care. Top three health risks: 1. Exposure to contaminants: 84 2. Exposure to disease and infections: 75 3. Time spent sitting: 67

Increasing awareness of long hours and high pressure jobs driving employee burnout, and cutting into time for recreation, exercise and family life have seen other employers follow suit.

In the US, where 80 per cent of large organisations and around half of midsize employers offer such schemes, health initiatives are also seen as a way to cut cost of long term illness borne by employer funded health insurance.

To test if wellness schemes were having a positive effect in the workplace, the Harvard team used data from 160 different employers and around 33,000 employees.

They picked 20 sites at random, with 4,037 employees in all, to act as a test group where wellness programmes were in place.

These employees were given eight learning modules on eating well, getting active and stress reduction and were supported by dieticians and an employee wellness provider over 18 months.

Apart from the increased exercise and weight loss, which are key measures for avoiding long-term health conditions like diabetes and heart disease, the study found no significant effects in 80 different areas.

Employees did not report better overall sleep quality, food choices or health, measures of blood pressure and other factors in regular health checks did not improve, nor did employer’s prescription costs and medical bills.

While these schemes may in future help motivate healthy behaviour, Dr Song said: “For now, however, we should remain cautious about our expectations from such interventions.”

Dr Jean Marie Abraham of the University of Minnesota, who was not involved in the Harvard study said there was increasing evidence of “limited or no effects” from these sorts of initiatives which should cause operators and employers to think about their offering.