When the normal circadian rhythms are disrupted by lack of sleep or by crossing time zones, it may take days or weeks for the body to readjust. Among the most common health problems are gastrointestinal complaints, including constipation, diarrhoea, excessive flatulence, abdominal pain and heartburn. These ailments are two to three times more frequent among shift workers. The causes are poor eating or diets high in saturated fats. Too much fast food is consumed because of constant tiredness and lack of time to prepare healthy foods.
People also have difficulty digesting food during the overnight hours.
Other factors include disturbed sleep, poor eating habits, overeating, excessive coffee drinking, smoking and psychological stress. Heart disease is an added risk. Increased consumption of fast foods, especially those high in fats, can increase cholesterol levels in the blood stream, leading to coronary heart disease. Higher levels of smoking among shift workers exacerbate the danger. The Helinski Heart Study of the Finnish population found that over a five-year period, rotating shift workers had a 40 to 50 percent increased risk of heart disease compared to day workers.