Obesity is a genuine problem in later life, and older adults face a particular version of it: mobility limits make exercise harder, dental and swallowing problems narrow food choices, and fixed incomes narrow them further. Low- and zero-calorie products look like an obvious solution, and diet soda is the most popular of them.
What the study found
The San Antonio Longitudinal Study of Aging followed 749 older adults over several years, recording diet soda consumption and measuring waist circumference. The results were published in the Journal of the American Geriatrics Society.
Diet soda drinkers showed substantially greater increases in waist circumference than non-drinkers — roughly three times the expansion over the study period. Waist circumference matters independently of overall weight: abdominal fat is more strongly linked to cardiovascular disease, type 2 diabetes and sleep apnea than fat elsewhere on the body.
What it does not establish
This is observational, and the obvious alternative explanation is hard to rule out: people who are already gaining weight, or who already have a diagnosis like diabetes, are precisely the people who switch to diet soda. The drink may be a marker of the problem rather than a cause of it.
Proposed mechanisms exist — effects on gut bacteria, on appetite regulation, on the learned relationship between sweetness and calories — but none is settled. What can be said fairly is that swapping to diet soda has not been shown to deliver the benefit people expect from it.
The broader point about “diet” foods
Diet soda is a specific case of a general pattern. Products marketed on the absence of one ingredient — sugar-free, fat-free, low-carb — tend to be judged healthy on that basis alone, and the substitution often turns out to deliver less than expected. For older adults the stakes are slightly different from the usual weight-loss framing: the risk is not only excess but displacement, where low-nutrition products crowd out food carrying the protein, fibre and micronutrients an ageing body needs more of, not less.
Someone eating too little protein while drinking three diet sodas a day has a nutrition problem that no amount of calorie counting will identify.
What this means for day-to-day care. Two practical notes. First, plain water is genuinely underrated: dehydration in older adults contributes to confusion, constipation, urinary infections and falls, and many people simply drink too little because getting to the bathroom is difficult. Making fluids easy to reach helps more than switching brands. Second, this is the person’s own home and their own choice — an attendant’s job is to support what they want, not to police their groceries.
Sources
- Journal of the American Geriatrics Society — Diet soda intake is associated with long-term increases in waist circumference in a biethnic cohort of older adults: the San Antonio Longitudinal Study of Aging
- World Health Organization — Obesity and overweight
- Mayo Clinic — Belly fat: why weight loss matters
This article is general information, not medical advice. It describes published research; it is not a recommendation for you or the person you care for. Never start, stop or change a prescribed medication because of something you read here — talk to the prescribing clinician first. Communicare Elite provides non-medical personal care through Missouri’s Consumer Directed Services program and does not provide medical advice or treatment.