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Top Doctor Reveals How to Use Intermittent Fasting to Lose Weight After 40

Millions of men and women above 40 struggle to shed their excess pounds, despite trying every type of diet under the sun and working out every week. 

Today, we give the floor to Dr. Jeffrey Collins, a double-board certified doctor and clinical nutritionist based in Boston. He will share with us how to drop weight for good using intermittent fasting, without creating feelings of hunger or depriving ourselves from the food we like.

“Hi, my name is Dr. Jeffrey Collins, I’m a certified nutritionist and doctor in the Boston area, and I spent the last 17 years of my life helping thousands of patients achieve radical and long-lasting body transformations. 

Dr. Jeffrey Collins talks about fasting

Most of my patients first come to me on the verge of despair… They tried every type of diet we keep hearing about online – Keto, Paleo, Weight Watchers, Atkins, Vegan, Dukan – you name it.

But no matter what they try, their problem is always the same: they start to lose a few pounds by depriving their body from the food they love, but at some point… their food cravings take over, and they ruin weeks of effort by jumping on their favorite snacks. 

At the end of the day, they end up gaining even more weight than they lost… And for most people, this weight loss “rollercoaster” can feel very discouraging. 

After seeing their “dream body” hopes smashed time and time again, people start to believe that something might be wrong with their body. When in fact the diets themselves are to blame, not them. 

Don’t get me wrong: most diets that we hear about (Keto, Paleo, Atkins, etc.) do work, to some extent. That’s why people generally lose a few pounds in the first weeks of adopting a new diet. 

The problem is that these diets are extremely hard to sustain over the long-term because they’re overly restrictive. We can tolerate them in the short-term, but at some point, our body rejects them because they don’t feel “natural”. This explains why 9 out 10 diets end up in failure today.

In my experience, and based on many discussions with fellow doctors and nutrition specialists, the diets that work are usually those that don’t feel like diets. In the sense that they don’t create any major resistance from our body, such as food cravings, hunger, or mood swings.

This Diet is Both Effective and Sustainable, According to Dr. Collins

The only effective diet that can be sustained in the long-term – and the one that I recommend to nearly all my patients – is intermittent fasting. And unlike what many people think, fasting doesn’t mean that we should starve ourselves to death – on the contrary! 

It just means that we should carefully choose WHEN we eat instead of being obsessed with WHAT we eat. You can eat pretty much whatever type of food you want, as long as you’re eating the right quantity of food at the right time.

The way intermittent fasting works is pretty simple. After fasting for more than 12 hours, our body has depleted all its glucose reserves and is forced to burn fat to find energy. When this fat burning “metabolic switch” is on, we lose weight effortlessly, without having to do crazy workout sessions or eating salad all day.

In fact, a recent study from Cambridge University has shown that our body starts burning fat about 25% faster after 13 hours of fasting [1]. 

Another review study conducted by researchers from Chicago in 2014 concluded that intermittent fasting could cause an 8% weight loss over 3-24 weeks – which was significantly higher than most weight loss studies on other diets [2]. 

People in the study also lost 4-7% of their waist circumference in a few weeks, showing how fast our body can melt during intermittent fasting or “IF” [2]. 

The proven weight loss benefits of IF explain why we see so many Hollywood celebrities practicing and publicly endorsing intermittent fasting!

What Other Doctors Think about Intermittent Fasting

“After 12 hours of fasting, insulin levels in our blood drop, allowing our bodies to burn more fat as fuel. This is helpful for patients who are insulin resistant, meaning their bodies make more insulin than normal. They may have tried healthy eating and exercise to shed pounds without success because their bodies are set to a fat-storage mode.”

Dr. Angela Fitch, MD, FACP, FOMA, Associate Director of the Massachusetts General Hospital Weight Center

“It takes 10 to 12 hours to use up the calories in the liver before a metabolic shift occurs to using stored fat. After meals, glucose is used for energy and fat is stored in fat tissue, but during fasts, once glucose is depleted, fat is broken down and used for energy.”

“Many things happen during intermittent fasting that can protect organs against chronic diseases like type 2 diabetes, heart disease, age-related neurodegenerative disorders, even inflammatory bowel disease and many cancers.”

Dr. Mark Mattson, neuroscientist at John Hopkins University, studied intermittent fasting for 25+ years

“When people lose weight, typically 75% is fat loss and 25% is muscle mass. But with fasting, the ratio actually changes so that 90% of weight loss is fat and 10% is muscle.”

Dr. Krista Varady, Associate Professor of kinesiology and nutrition at the University of Illinois, Chicago

Harvard logo

There is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective.[3]

Dr Deborah Wexler, Associate Professor at Harvard Medical School

How To Lose Weight Fast Using Intermittent Fasting?

While many doctors agree on the effectiveness of intermittent fasting in helping us lose weight, many people don’t know how to integrate this diet in their daily life. So we asked Dr. Collins about the “best practices” of intermittent fasting.

“To obtain the best possible results, I recommend following a personalized intermittent fasting plan prepared by professional nutritionists. 

Because in my experience, people who try intermittent fasting by themselves may obtain visible results, but the diet can be hard to implement properly without precise instructions, including what to eat and at which time exactly… 

Further, each of us has a unique metabolism. So if we want to lose fat, we need a tailor-made plan suited to our exact metabolic needs as well as food preferences. IF diets that follow one-size-fits-all approaches are highly likely to fail…

The personalized intermittent fasting plan that I recommend to nearly all my patients is the “DoFasting” plan. In this plan, professional nutritionists personalize everything for you based on your daily schedule, unique eating preferences, age, weight, and so on. 

Clinically speaking, this bespoke, scientific approach to intermittent fasting is an effective way to melt fat, without yo-yo effect.

All my patients have told me that this plan was very easy to follow in the long-term, and that it quickly became “second nature” right after the first week. 

Unlike other diets which often require lifestyle sacrifices, this diet plan adapts itself to the lifestyle of the user. So it offers unparalleled flexibility.

Another key benefit of this diet plan – and the reason it works so well in my view – is the fact that it doesn’t make the user feel deprived or hungry. 

It is designed for the user to eat according to their hunger, but to eat at times during the day that maximize metabolic fat burning. 

So I think that anyone interested in intermittent fasting should probably have a go at this plan, which is thoroughly designed and fully in line with nutritional best practices.”

Today, the DoFasting team offers a free 60-second quiz to help you discover which fasting schedule would best suit you, based on your own individual preferences and lifestyle.

Access this quiz now while it’s still available by clicking on the button below:

Take a quick 60-second quiz and discover which fasting schedule best suits you to lose weight

Results may vary due to personal features.


  1. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-aerobic-exercise-performed-in-fasted-v-fed-state-on-fat-and-carbohydrate-metabolism-in-adults-a-systematic-review-and-metaanalysis/0EA2328A0FF91703C95FD39A38716811
  2. https://www.sciencedirect.com/science/article/abs/pii/S193152441400200X
  3. https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156


  1. Tried it, works for me.

  2. Started IF last week, I already see a change in my body. Excited to continue!

  3. I was a bit skeptical at first given how many times I failed to lose weight using new diets… but having tried intermittent fasting for over three months, I must say this is legit! It took me about a week to get used to the diet. But after that, I noticed visible weight losses which I haven’t regained since. I went from 174 lbs to 153 lbs, and I continue to see my body getting slimmer over time, without feeling hungrier than usual. I don’t see myself returning to a normal diet now.

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