I have a wonderful workout partner, who is also a very close friend. He is totally worked out and knows what to do. He's designed my workouts and is there with me on two of the three days that I work out. He's inspirational and doesn't let me get away with lazy form. For my part, I have learned how to be an excellent spotter for him.
Since November, he's put me on the same diet that he;s on. Actually, not a diet, since he hasn't modified much. What he's done is cut out all alcohol except on days on which you are with other people (for example, out to dinner with friends or holidays). That means, when you are home alone, no beer with dinner.
No desserts except on occasions (not difficult for me, since I rarely have desserts), and no cheese on sandwiches (though it's OK on pasta etc.).
I am running 50 miles per week as a separate issue, but just adding him back as a workout partner plus his diet....I have lost 6 pounds since November 3rd, and it shows.