Older adults who ate more protein while losing weight had more lean tissue in their arms and legs, but the extra protein showed no link to their strength or walking speed, according to a 2026 analysis of three clinical trials published in Nutrition Journal.
The finding adds to research on muscle loss during weight loss, which the authors tie to sarcopenia, the age-related loss of muscle mass and function that weight loss can worsen. They suggest strength and walking speed may depend more on resistance training than on protein.
The authors note that about 25% of the body mass lost in weight loss interventions is fat-free mass, a particular challenge for older adults already experiencing age-related declines in muscle.
The analysis pooled data on 191 adults aged 55 and older with overweight or obesity, with a mean age of 65. All participants followed diets designed to provide about 600 calories a day below estimated energy needs and performed resistance training for 10 to 13 weeks. Dual-energy X-ray absorptiometry (DXA) scans measured the lean tissue in their arms and legs.
Two of the trials tested a daily supplement of whey protein, leucine and vitamin D that added about 21 grams of protein. The third included a counseling arm aimed at about 1.3 grams of protein per kilogram of body weight a day from ordinary food.
Participants in those arms raised their intake from 0.89 to 1.12 grams per kilogram a day, while intake in the other arms changed little, from 0.88 to 0.83. Each additional 0.1 gram of protein per kilogram of body weight per day was associated with about 0.1 kilogram more lean tissue. Protein intake showed no association with body weight, body fat, handgrip strength, gait speed or a chair-stand test.
The recommended dietary allowance for protein is 0.8 grams per kilogram a day. The authors write that older adults losing weight while doing resistance training are believed to need more, and an exploratory analysis of one of the trials pointed to at least 1.2 grams per kilogram of body weight per day. They describe the optimal intake as unsettled.
The analysis relied on self-reported food records, which people with overweight may underreport, though the authors add that those records tracked closely with a urine-based measure of protein intake. The three trials were chosen based on availability, and all ran at the Amsterdam Nutritional Assessment Center at the Amsterdam University of Applied Sciences.
Trilivy™, a science-backed, coach-guided comprehensive metabolic health system, describes a metabolic health program as one that targets the system behind the weight, including fat storage and lean mass, and aims to reduce visceral fat while preserving metabolically active muscle.
“Weight loss was never the whole story, just the most visible one,” said Satya Jonnalagadda, PhD, MBA, RD, Vice President, Scientific & Clinical Affairs at Trilivy. “When a program treats the scale as the only target, it can miss the metabolic dysfunction that decides whether progress is made or slips away.”
Medifast funded a 16-week randomized controlled trial of 198 adults with overweight or obesity, published in Obesity Science & Practice in 2019. It tested the plan under its former name, the OPTAVIA 5&1 Plan, with telephone coaching, and measured fat and lean mass by DXA. Participants had a mean age of 45.7, so this was not a trial specifically of older adults. The company reports that participants on what is now the Reset 5 & 1 Plan retained 98% of their lean mass at 16 weeks.* It describes lean mass as the tissue that determines resting metabolic rate. Results in the trial reflect the plan and its coaching support working together.
“A weight management program that protects lean mass, reduces visceral fat, and builds habit infrastructure is designed for the years after the active weight loss phase and addresses the conditions that drive regain at the source,” said Satya Jonnalagadda.
The 2026 analysis covered that active weight loss phase only, with trials lasting 10 to 13 weeks. Older adults who ate more protein while losing weight had more lean tissue in their arms and legs, a difference DXA scans detected even though protein intake showed no link to body weight. The authors describe the optimal protein intake for this group as unsettled. The findings fit the emphasis Trilivy places on protecting lean mass during weight loss and on body composition as a measure of progress, since a scale cannot separate lean tissue from fat.
* Trilivy™ recommends that you contact your healthcare provider before starting and throughout your weight loss journey.
* Arterburn LM, et al. Randomized controlled trial assessing two commercial weight loss programs in adults with overweight or obesity. Obesity Science & Practice. 2019. https://onlinelibrary.wiley.com/doi/10.1002/osp4.312. In a clinical study, individuals on the Reset 5 & 1 Plan experienced a reduction of 14% visceral fat and 98% of lean mass was retained at 16 weeks.
