Consultants do work long hours. Not as bad as investment bankers though. In my opinion, it takes a conscious effort to have a healthy lifestyle in consulting. Presuming that the focus on health is mostly on physical exercise and diet (versus mental health or social relationships), here are some things I’ve used to try to strike a balance:

• On the job, really focus on what is strategically important; try to cut bait or minimize involvement with small stuff that you shouldn’t sweat. An end goal might be to target roughly 60 hours of work per week on average, and that requires prioritization and efficiency.
• Try to use facilitative consulting methods where possible versus having to deliver content directly. There are two benefits to this (but it depends on the engagement). Facilitative consulting tends to leave a client organization in a better state where things stick (tends to decrease long-term dependency on the consulting firm). The consulting firm can also get better leverage. The thing to watch out for the facilitativre approach is that sometimes the client organization expects the consulting firm to do things for them, even though this might not be in the client’s best interest (e.g., imagine hiring an exercise coach where the coach spends all the time demonstrating exercises; yes you’ve paid them, but eventually it is you that needs to exercise).
• Learn how to execute on an effective, reasonably rounded, exercise program in 30–45 minutes (e.g., cardio, abs, legs, arms workout areas). Could be 3 sets of 2–3 exercises per workout area with some rotation of programs. Perhaps get a physical trainer to come to your house on the weekends to get you in the flow. And cover cases where you need to use minimal equipment (in case gym access is limited). Get a buddy, such as running with a colleague or client. Although this one might add weight to your rollerboard, here’s an example of a workout that can be done with two, five-pound dumbells:
• Since you often have to eat out a lot, consider eating lunch at healthier places, even at salad bars with grocery stores (like Whole Foods). Figure out how to reduce carbs and meat intake if possible (perhaps by getting client recommendations for places to eat). Drink plenty of water.