Obesity is common in older persons, increasing the risk of disability. Modest weight loss achieved by hypocaloric diet and exercise has been shown to improve physical function, cardiovascular risk, glycaemic control and cognition. However, this approach may not be sufficient in people who are significantly obese or dependent on care. Use of ketogenic very low energy diets (VLEDs) that achieve greater weight loss have not been studied in older people. Ketosis has theoretical benefits relevant to older people; namely improvement in cognition and retention of lean mass.
A 12 week randomised controlled trial compared healthy eating advice, hypocaloric diet and VLEDs, all combined with exercise. 93 people participated. At baseline and completion, tests of physical function (6 minute walk test, de Morton Mobility Index), cognitive function (processing speed, executive function, verbal fluency), DEXA for body composition, glycaemic, cardiovascular and nutritional markers were performed.
Loss of weight, muscle and fat mass was greatest in the VLED group. However, fat mass was greater than muscle mass, such that percentage muscle mass improved by the greatest degree. The VLED group had the greatest improvements in systolic blood pressure, HBA1C and triglycerides of the three groups there were improvements in cognitive parameters in all three groups, but no difference between the three groups in degree of improvement. The VLED group had the greatest increases in nutritional parameters (vitamin D, B12, folate and ferritin). Physical function improved equally in all three groups; the improvement was inversely proportional to baseline physical function. VLEDs had similar side effects in this older group compared with in younger adults.
VLEDs are safe in older persons, with predictable side effects. The changes in body composition, nutritional profile, blood pressure, triglycerides and HbA1C are all favourable compared with healthy eating advice or hypocaloric diet.