Dr. Krista Varady Ph.D. is a gosh darn genius. In 2006, while we were all off in low-fat la la land, stuffing our faces with high-carb treats, watching the Charmed finale (and wiping said faces on our pyjama sleeves), she was hard at work researching the effects of fasting. Dr. Varady is an associate professor of awesomeness* (and nutrition) at the University of Illinois-Chicago, and she is the global go-to for intermittent fasting research. She’s been studying the effects of fasting on humans for more than 10 years, and she literally wrote the book on alternate day fasting. (It’s called The Every Other Day Diet, for those of you who want homework.) She talks us through how she came to study intermittent fasting.
* Not a real position. Although, wouldn’t it be cool if it was?!
The start of her Intermittent Fasting Research
I became interested in researching intermittent fasting when I started my post-doctorate position at the University of California Berkeley in 2006. At first, I was interested in seeing if cancer risk would decrease in mice who were fasted, but who did not lose weight. To put it another way: I was interested in seeing if I could tease apart the effects of fasting versus the effects of weight loss.
Why did I want to do this? Well, when a person (or a mouse!) fasts and loses weight, pretty much all of the beneficial health effects are due to weight loss. Losing weight is a very powerful thing. Just small amounts of weight loss can drastically decrease a person’s risk of developing heart disease, diabetes, or cancer. So, in short, I was interested in seeing how fasting alone, without weight loss, could impact the risk of cancer and other diseases.
The failed experiments
When I started my experiments, I struggled a little with how to fast a group of mice and not have them lose any weight. I thought perhaps I could have the mice not eat anything one day, then allow them to eat to their heart’s content the next.
Unfortunately, that didn’t work. All of the mice lost weight.
Then I tried feeding the mice a small amount of food on the ‘fast day’, and letting them binge on food on the ‘feast day’. That didn’t work either. The mice still kept losing weight! I ended up feeding the mice almost half of their daily calorie needs on the fast day, and they still lost weight! I was amazed (and also a little disappointed, because – as I saw it – my experiments had failed).
The A-HA moment: Intermittent Fasting leads to weight loss
Then it occurred to me: weight loss isn’t always a bad thing! Maybe this diet could help individuals with obesity lose weight and decrease their risk of chronic disease?
I immediately began a whole new set of experiments that focused solely on how people responded to intermittent fasting. To be honest, I wasn’t entirely sure the diet would work in human subjects. For instance, would an individual with obesity really be able to decrease their food intake to 500 calories every other day? Would they even want to do this? And how long could they sustain this eating pattern?
I was blown away when the results of our first human study showed that people found intermittent fasting to be pretty easy. Our subjects were able to stick to the 500-calorie goal on approximately 90% of fast days (read the papers here and here).
Lots of individuals reported loving the simplicity of the diet and the ability to eat freely every other day. On top of that, they were also losing lots of weight! In this 8-week study, 15% of people lost 10 kg and above, and 45% lost 5 kg and above.
I knew that we were on to something. Something big.
Intermittent Fasting Research so far
Since then, I have run about a dozen intermittent fasting studies in human subjects (see here, here and here), and they all show the same thing: people find the diet easy to follow, they lose weight, and their risk of heart disease and diabetes decreases. In general, our studies have shown that 10% of subjects lose 15 kg and above, 15% lose 10 kg and above, and 40% lose 5 kg and above.
Our findings also show that alternate day fasting can help people reduce bad LDL cholesterol levels (studies here, here and here), triglycerides (read here and here), blood pressure (read here and here), and increase good HDL cholesterol levels (read here and here).
I am currently in the process of running longer-term studies to see if people can use intermittent fasting to maintain weight loss and sustain reductions in chronic disease risk. We will be sure to share the results of these studies as soon as they are published!
Dr Krista Varady has leant her powerful brain to us for another blog on the science-backed health benefits of Intermittent Fasting. We’ll be sharing it on the Superblog this Friday. Stay tuned!