Ask A Dietitian: What’s the Deal with Intermittent Fasting?

*This post deals with intermittent fasting and smoothie making.

One of the many advantages to joining the Cooking Light Diet is having access to our staff of professionals. In particular, members can tap into the expertise of our James Beard Award-winning lead dietitian, Carolyn Williams, PhD, RD, who’s been an instrumental part of the team since we launched our service in 2014. 

As part of an effort to provide members with even more serviceable content to assist their respective journeys to good health, Dr. Williams will be answering questions posted in our Facebook Community.

We wanted to know: If you could ask a dietitian anything, what would you ask? This is part four of an ongoing series.

Cooking Light Diet member Cyndie Moran asked,

“There seems to be a lot of buzz around time-restricted eating and other forms of intermittent fasting that limit eating to a certain number of hours during the day. Is there any benefit or downside to incorporating this into my meal planning?” 

I’m really cautious when it comes to nutrition trends, but intermittent fasting is something that’s intrigued me ever since I started following research studies a few years ago to look at potential benefits and health effects.

If you’re not familiar with intermittent fasting, check out my Cooking Light article which details the most common fasting methods (such as 16:8 and 5:2) and answers common questions regarding how fasting affects metabolism.

The consensus? It turns out that going longer periods between meals and snacks in a 24-hour period may have a positive effect on health numbers for some individuals.

There’s no reason why you can’t incorporate a 16:8 intermittent fasting approach into your Cooking Light Diet meal plan, though, if you want to give it a try.

To do this, I suggest either pushing back breakfast to when your 8-hour eating window starts, or skipping breakfast and eating an equivalent amount of calories later in the day as a snack.

Remember: The goal isn’t to drastically cut calories, but rather to consume appropriate amounts of calories and nutrients—just within an 8-hour window.

I’ve also recently started following a 16:8 fasting approach—something I started more as a science experiment to see what it was like.

To my surprise, I’ve ended up sticking with it because I like the affects I feel in regards to reduced hunger and cravings, more stable blood sugar, and improved energy.

However, fasting isn’t for everyone, so if the concept sounds dreadful, skip it and move on. No one should feel pressure to incorporate it into their current eating routine, and there are some medical conditions where it may not be recommended.

Cooking Light Diet member Joanne Zuccaro Devaney asked,

When I make a smoothie without a recipe, how can I choose ingredients and amounts so I don’t create a calorie bomb?

Smoothies are one of my favorite quick meals to make—especially in warmer months—but they can quickly turn into calorie bombs if you’re not careful. Here’s my unofficial guideline for keeping smoothies in check.


My first ingredient is always some type of frozen fruit, but I tend to be partial to be partial to berries. Berries are low in calories, packed in antioxidants and fiber, and create a vibrant color and flavor. All this to say, you often don’t need a lot of extra sugar or ingredients when berries are in the mix.

You can’t go wrong with blueberries, strawberries, berry blends, or cherries as long as you’re buying them without added syrup or sweeteners. A cup of berries has approximately 60 calories and 3-6 grams of fiber, so don’t be afraid to use 1 to 1 1/2 cups.


Protein per serving is often the first nutrient I check when considering a new smoothie recipe. I like to see that one serving provides around 10g protein—particularly when the smoothie is replacing a meal.

Without that, you’ve got a liquid meal that’s predominantly carbs and won’t stick with you as long. Some quick options for adding 8 to 12 grams of protein while keeping calories in check are:

  • 1/2 to 3/4 cups of plain Greek yogurt, a filtered milk (such as Fairlife) that’s slightly higher in protein than regular dairy, or soft tofu;
  • 3 to 4 Tbsp. unsweetened or plain protein powder;
  • 3/4 to 1 cup non-dairy plain yogurts (check protein on labels since amounts can vary greatly in non-dairy versions);
  • or a combination of proteins like 1 Tbsp. nut butter and a little milk.

Always taste before assuming a smoothie needs sweetness. If needed, I’ll often add a half to a whole ripe banana for a little natural sweetness.

You can also opt for added sugar sources like honey or maple syrup but remember that these contribute about 60 calories per tablespoon. Another calorie-free option for some is to add a touch of liquid stevia.


Adding enough—but not too much—liquid is the key to get that perfect smoothie texture. Unless the liquid you’re adding is also your protein source (such as milk), opt for a liquid that has less than 40 calories per cup.

Unsweetened vanilla almond milk, water with a splash of juice, or coconut water all have a slight hint of sweetness with very minimal calories. I try to avoid using more than 1/4 to 1/3 cup of fruit juice to keep calories in check.

Members following the Cooking Light Diet, on average, lose more than 1/2 lb. per week.

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