The latest research shows the best results were achieved by combining aerobic (such as walking, swimming, and bike riding) and resistance (such as weight lifting) exercise routine.

Dr. Dennis T. Villareal from the Baylor College of Medicine in Houston, TX and colleagues studied the responses of 160 older (over 65) obese people (BMI > 30) to resistance training, aerobic training or a combination of the two types during a 6-month weight loss regime. Most of the participants were female (over 60 percent) and 90 percent were white. The primary outcome the investigators were interested in was any changes in participants' performances on the Physical Performance Test (PPT). This involved tasks such as putting on and taking off a coat, walking a specified distance, picking up a penny, as well as balance tests — all actions which revealed the extent of deficits in physical functioning and possible degree of frailty. In addition, they examined changes in body weight, peak oxygen consumption (a measure of fitness), and a number of other parameters.

After 6 months on their respective regimes, all the groups improved their performance on the PPT, but the improvement was greatest in the combination aerobic and resistance group — 21 percent — significantly greater than any of the other groups. In contrast, the control group's PPT score increased by 4 percent, and the resistance and aerobic groups increased by 14 percent each. All the exercise groups lost a similar amount of weight — 8.5 to 9.0 kgm (19-20 lb), which was a significant difference from their baseline weights. They did not differ from each other, however. And the control group's weight didn't change significantly.

Peak oxygen utilization also increased significantly in the exercise groups, but not in the control group. Further, both the combination and aerobic exercise groups' change in peak oxygen utilization were significantly greater than than that of the resistance group.

http://www.acsh.org/news/2017/05/25/both-resistance-and-aerobic-exercise-good-older-obese-people-—-especially-when-combined-11331

Interesting, so would that mean that the resistance-only group would have a lower metabolism and therefore eventually lose less weight if they kept going with their assigned programs (since their respiration utilization was lower)?