But she says when we do such things can have a big impact on how much we get out of them.
"For certain things, timing can make a difference, and you may reap greater benefits if you time them just right," Marshall says. "Remember, our bodies function on a internal clock. That is - we have a particular body rhythm which to some extent is out of our control. Also, for certain things, there are external factors beyond our control. So timing can mean everything."
Marshall offered advice on how to maximize the benefits of several common health-related activities:
TAKING A NAP
Research shows that taking an afternoon nap, especially for people who don't get enough sleep at night, can really be beneficial for the body and mind. According to some experts, the best time to take a siesta is early afternoon, say, between 1:00 and 3:00 pm. That's because your body temperature tends to dip at this time and you're more likely to fall asleep and be less alert. You should only snooze for 15-20 minutes though, because that's long enough to perk you up - while a longer nap can make you fall into a deep sleep and make you even groggier.
Of course, exercising at any time of day is better than no exercise at all. And many people like the routine of working out in the morning before work. But some experts believe it's best to exercise in early evening. At that time, your muscles are already warmed up, you're coordinated and less likely to sustain an injury. Also, if you're all stressed out at the end of the day, evening exercise can provide a great stress reducer and help you get a better night's rest. But whatever time you choose, consistency matters most.
The best time to take a multivitamin is with a meal. That's because taking a vitamin on an empty stomach can cause nausea and indigestion. Most experts say it doesn't matter whether you take it with breakfast, lunch or dinner - but some say breakfast is best, because you're more likely to consistently eat breakfast at home and it will help remind you to take your vitamin every day.
There is no simple rule for this. It really depends on the medication. That's why you want to ask your doctor or pharmacist whether it's better to take a certain drug with or without meals, in the morning or at bedtime, etc. For example, ibuprofen should be taken with food so it doesn't upset your stomach and diuretics or water pills are best taken early in the day. And it's important to take certain medicines at a consistent time every day.
VISITING THE DOCTOR
Like most people, I hate having to sit in the waiting room for a long period of time. So if you really want the best chance of being seen at or near your appointment time, the best time to go is first thing in the morning or right after lunch, when they're less likely to be behind schedule and less likely to feel harried. And if you need to have blood tests done, you may want to do it first thing in the morning in case they need a fasting sample.
EATING YOUR BIGGEST MEAL OF THE DAY
Most nutrition experts would agree that it's best to eat smaller meals throughout the day than to rely heavily on one big meal. This helps curb any food cravings and maintain a healthy body weight. So try to eat a small breakfast, lunch and dinner and a couple of healthy snacks in between. And if you're going to schedule a bigger meal, earlier in the day is better, so you have a chance to burn off some of the calories before your go to bed.
BRUSHING YOUR TEETH
Most of us brush our teeth as soon as we wake up and before bed. If you eat breakfast at home, wait to brush your teeth until after your morning java. Also, try to give your teeth a quick brush after all meals. And if you're only going to give your teeth one good scrubbing a day, save it for bedtime to avoid plaque build-up and decay overnight.