Partners who only came along to help lost more weight.

People say: “Does a weight program help the partner too?” We read the study.

What they did

Randomised controlled trial (RCT). 231 couples. 24 months (6-month weight-loss phase, 12-month maintenance phase, 6 months with no intervention).

A trial. Chance decided who did what.

Who: 231 cohabiting romantic partners (US, University of Wisconsin trial) of adults with BMI >= 27 enrolled in a weight program; partners mean age 48.3, 63% men, 88% White, 87% married, mean BMI 32, relatively high socioeconomic status

What they found
  • Partner who joined-2.0 kgmore than at home
  • Lost 5% of weight37%vs 20% at home
  • Calories eatennoneno clear change
The catch

More to know, from our read of the paper:

  • Secondary analysis: the trial was powered on the index participants' weight, not the partners'
  • Only 68.7% (partner-assisted) and 77.6% (participant-only) of partners gave 24-month weights; those missing were heavier and had lost less earlier. Multiple imputation (counting dropouts) made the difference larger (-2.7 kg, CI -5.1 to -0.3), and unconstrained models agreed (-2.2 and -2.9 kg)
  • Group differences at 6, 12 and 18 months were smaller and not statistically significant; the effect only reached significance at 24 months
  • Partners in the partner-assisted group happened to be heavier at baseline (100.2 vs 94.9 kg, 33.9% vs 21.5% BMI >= 35)
  • The 37% vs 20% reaching 5% weight loss is descriptive (no inferential test)
The verdict

Partners who joined in lost more weight.

One thing to try
  1. Go alongPartners who joined lost 2 kg more.
In short

In a US randomized trial, 231 couples were split into two groups. In both, one person did a two-year weight program; in one group their partner also came to about half the sessions, only to support them. After 24 months, partners who joined lost 2.5 kg on average versus 0.4 kg for partners who stayed home, a 2 kg difference, and 37% versus 20% lost at least 5% of their weight. Self-reported calories showed no clear difference, and the people in the program lost a similar amount in both groups.

The video
The paper

Gray KE, Porter LS, Shaw RJ, Gavin KL, Hetzel SJ, Lewis MA, Pabich S, Johnson HM, Elwert F, Mao L, Garza K, Yancy WS Jr, Voils CI (2026). Partner Weight Loss and Diet Outcomes at 24 Months in a Randomized Controlled Trial of a Dyadic Versus Individual Weight Management Intervention. Obesity Science & Practice.

Design: Randomised controlled trial (RCT) · secondary analysis of partner outcomes in a two-arm parallel randomized controlled trial (Partner2Lose, NCT03801174), randomized by couple; intention-to-treat linear mixed models

DOI: 10.1002/osp4.70178

Goals:

Eat better
How we checked

We read the abstract and the full text of this paper and checked every number on this page against it (17 facts, checked on 2026-10-29). The study design is named above. Cohort and other observational studies are described as linked, not proven. Found an error? Email theis@onestudyaday.com.

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