Less fat inside the thigh muscles, a stronger grip? A low-carb trial in people over 60, run in 2015 and funded by egg money, reports its strength results nine years on

As we age, fat doesn't only collect under the skin and around the belly. It also creeps in between and inside the muscles, like marbling in a steak. Researchers call it intermuscular adipose tissue, and in older adults more of it goes with weaker, slower muscles and more trouble getting around. So a diet that could clear some of it out would be worth knowing about.

A paper published in Obesity on 6 October 2026 by a team at the University of Alabama at Birmingham says a very low-carbohydrate diet might be that diet. Adults aged 60 and over with obesity were randomised to eight weeks of either a very low-carb diet (under 10% of calories from carbohydrate) or a low-fat diet (55% from carbohydrate). MRI scans of the thigh showed the fat inside the muscle fell by 24.4% on low-carb and by 1.0% on low-fat. Across everyone in the trial, people who lost more of that fat gained more grip strength, more knee strength and a better reach score, even after allowing for changes in muscle size and body weight. The authors conclude that diets which shrink this fat, such as a very low-carb diet, may help older adults keep their strength and function.

The new paper is a secondary analysis, and the trial behind it is not new. It ran from January 2015 to July 2017. Its main results came out in 2020 in Nutrition & Metabolism, an open-access journal, so anyone can read the details. The 24.4% versus 1.0% figure is already there, six years earlier. What the 2026 paper adds is the link to strength and function.

The 2020 paper fills in what the new abstract leaves out. Forty people were randomised and 34 finished: 19 on low-carb and 15 on low-fat. The six who dropped out were all women aged 67 to 72. The low-carb group were asked to eat three whole eggs a day and were handed two dozen eggs a week; the low-fat group were asked to avoid whole eggs and were given breakfast bars. The trial was funded by the Egg Nutrition Center, and its ClinicalTrials.gov record, titled 'Does an Egg-Rich Diet Improve Metabolic Health and Function in Obese Older Adults', lists the American Egg Board as a collaborator.

The new abstract calls the diets 'weight-maintaining'. That's what they were meant to be: the dietitians drew up meal plans to keep weight steady and nobody was told to cut calories. But it isn't what happened. In the 2020 paper the low-carb group lost 6.3% of their body weight in eight weeks, about 6 kg on average, against 1.0% on low-fat, and 9.7% of their body fat against 2.0%. The authors wrote that the low-carb group 'spontaneously restricted intake'. So the low-carb group were on a weight-loss diet in practice, and part of the drop in muscle fat may simply be what weight loss does. In the 2020 analysis the gap in thigh muscle fat did hold up after allowing for fat lost (p = 0.02), which suggests it was more than weight loss alone, though in a trial this small that is one test, not a settled answer.

There is a quieter detail in the 2020 table. At the start, the low-carb group had more fat inside their thigh muscles than the low-fat group: 20.9 cubic centimetres on average against 15.1. After eight weeks the low-carb group were at 15.8 and the low-fat group at 15.7. The low-carb group lost a lot, but they also started with more to lose, and both groups ended up in almost the same place.

Then there are the strength figures. The abstract reports that change in thigh muscle fat 'explained' 95% of the variation in change in grip strength (r² = 0.95), 88% for knee strength and 75% for reach. In a few dozen people, over eight weeks, with a test as variable as a grip squeeze, 95% would be remarkable. Because the models were adjusted for muscle volume and body weight, these figures may describe how well the whole model fits rather than thigh fat alone; we couldn't check, because the full paper is behind a paywall. Notice too what the abstract doesn't say: whether the low-carb group actually ended up stronger, or walked further in six minutes, than the low-fat group. Links found across everyone in a trial are not the same as an effect of the diet.

None of this makes the finding wrong. Fat inside muscle is a sensible target in later life, and the MRI scans were analysed by staff who didn't know which diet people were on. But this is a small, unblinded, eight-week trial with a sponsor whose product was the centrepiece of one diet, reported in two papers nine years apart. Whether cutting carbohydrate keeps older people stronger needs a bigger, longer trial with strength and walking as its main measures, and diets matched for weight loss.