The Obesity Code, written by Dr. Jason Fung, MD, is a book about the obesity epidemic and how there is a secret to unlocking the code to weight loss.
As explained by health and medical writer Jane Langille, obesity is a hormonal disorder of fat regulation. Insulin and insulin resistance play a large part in weight loss and weight gain over time. 
Dr. Fung is a kidney specialist with a focus in treating people with type 2 diabetes and obesity in general, so his wealth of knowledge on this subject is seen throughout the read. The Obesity Code talks about how insulin, insulin resistance, and hormones, rather than calorie intake or expenditure, make all the difference when you are trying to lose weight—whether you are obese or only slightly overweight.
Originally published in March of 2016, The Obesity Code talks about giving your body the ultimate break from the highs and lows that insulin levels can produce. The idea of fasting is one of the main ways you can give your body a break from these highs and lows. Fasting is a big point of discussion throughout the chapters, and it doesn’t matter whether you are fasting 16 hours, 20 hours, or longer, because Dr. Fung believes that weight loss is achieved by eating less, versus eating smaller meals more frequently. The idea to not snack is also thrown out there, because your insulin will always be responding to your snacks, which in turn can cause fat to hang on for longer. Dr. Fung also does not believe in breakfast, and thinks it can be optional—or at least the timing on it can be pushed back:
The French, a notoriously skinny people, have another word for breakfast—petit déjeuner, which means “little lunch.” So, many French people routinely skip the meal and just drink coffee and break their fast at lunchtime. And guess what? There is nothing wrong with that. The breakfast meal can be taken at 12:00 instead of 8:00. 
The Obesity Code Claims
About The Author
Jason Fung is from Toronto, Canada, where he maintains a practice. As stated above, he is a type 2 diabetes specialist and founder of the Intensive Dietary Management Program. This program provides help and guidance, not only to type 2 diabetics but also to people who are obese and pre-diabetic. His research relies solely on journal evidence, and he is concerned the leading cause of these diseases is only from the Western diet. The good news, according to Dr. Fung, is that any disease caused by diet can be fixed with diet. 
What Foods Are Advised?
The Obesity Code gives a pretty basic overview of what foods are allowed while going through this diet, although it does not offer a specific eating plan. Many of these foods everyone already knows are good for your overall health, so this list did not come as much of a surprise to me.
- foods without added sugar;
- healthy fats;
- healthy carbohydrates like whole grains, fresh fruit, and fresh vegetables;
- and pretty much anything unprocessed.
He also suggests limiting proteins, because they naturally cause an insulin increase in the body. Lastly, he says to limit refined carbohydrates (white rice, white flours, white sugars, etc) due to their insulin response as well (moreso than the protein, even). And snacking, even healthy snacking, is a no-no. The idea is to give your system a rest.
One key to this book is the timing of eating, as well as eliminating your snacking altogether. When you snack your glucose levels raise up, which the body then uses for energy and burning. If you do not have those glucose levels rising every hour the body burns fat instead, which will ultimately cause weight loss as explained by Dr. Fung.
When asked what causes obesity, Dr. Fung stated:
It turns out that the problem with obesity is a poor distribution of energy, not the amount. Food energy is being diverted into fat storage instead of being used up. Insulin is the major hormonal regulator of this process. Excessive insulin causes obesity. 
His claim about breakfast was rather alarming, because this is a rather controversial topic for many people. But Dr. Fung claims you can skip right over breakfast—though you can have coffee or tea or water—and add it to your “fasting hours” and be just fine for weight loss. What many people find is that they are starving mid-morning if they do not eat breakfast which causes them to slip up and eat something unhealthy. But I suppose enough water could keep you feeling full until lunch, even if it takes you to the restroom a lot.
Dr. Fung says:
If you have more weight to lose, you can simply extend the fasting period. Instead of 12 hours, you can extend this to 16, or even 24 or 36 hours. This is the process called intermittent fasting. A common regimen would be to use a 24-hour fast (from dinner to dinner, for example) twice a week. 
While it might not work for everyone, it has been looked into as effective for those needing to lose large amounts of weight.
This isn’t a full-on daily fast. The Obesity Code recommends that fasting should occur at least twice throughout the week, for 24-hour periods. You keep hydrated by drinking water, green tea, and coffee, so you will be putting something in your body throughout those 24 hours. And on non-fast days, or in general, snacking is not advised at all while you are following the code. 
The Science (or Lack Thereof) Behind The Obesity Code
Because there is so much talk about Intermittent Fasting, I wanted to take a look at some of the studies that were done around it. Some of the concerns with intermittent fasting occur when people binge eat after the temporary fast is over, which can cause rapid weight gain if you are not careful.
According to a meta-study published in the June 2013 Canadian Medical Association Journal, several different trials were conducted on a variety of people with ailments like diabetes and obesity to see how intermittent fasting affected those people. Their findings?
Mattson and colleagues explored the effects of intermittent and continuous energy restriction on weight loss and various biomarkers (for conditions including breast cancer, diabetes and cardiovascular disease) among young overweight women. They found that intermittent restriction was as effective as continuous restriction for improving weight loss, insulin sensitivity and other health biomarkers. 
Mattson has also researched the protective benefits of fasting to neurons. If you don’t eat for 10–16 hours, your body will go to its fat stores for energy, and fatty acids called ketones will be released into the bloodstream. This has been shown to protect memory and learning functionality, says Mattson, as well as slow disease processes in the brain. 
This essentially proved Dr. Fung’s overall point from his book, and sets the overall tone for how the book should be followed. In similar studies done on people with asthma and cardiovascular stress, there was a noticeable amount of reduced inflammation throughout the body when it came to letting the body rest with intermittent fasting.
Instead of looking at intermittent fasting as a “diet,” it is rather referred to as a “schedule.” According to another study cited in a sports medicine article, the intermittent fasting state does not come naturally or easy by any means and there could potentially be side effects.
Indeed, with any method, there is a critical transition period of about 3-6 weeks during which the body and brain adapt to the new eating schedule (Longo and Mattson, 2014). This period can be very uncomfortable, as restricted eating has been anecdotally associated with extreme hunger, irritability, loss of strength, loss of libido, and other negative side effects (Dirks and Leeuwenburgh 2006; Johnstone 2007; Heilbronn, Smith, et al. 2005). 
But if you can get past the initial stage of fasting, you will see more positive results.
Word On The Street About The Obesity Code
On Amazon.com, customer reviews were 93 percent positive to only 3 percent negative. 
The overall vibe from happy customers was simply that the book was very informational and easy to get through. The few who had negative comments simply thought that intermittent fasting was spoken about with no other real substance to the book made it boring to get through. Others thought the book encouraged unhealthy fasting, which is up for debate.
“chungking” (October 2017, 5 stars) said:
Dr. Fung’s prescription of fasting, explained in his book, and on his blog and podcasts, immediately worked for me. It is simple to understand and follow, and has been life-changing. I’m not sure what I can add to 1000+ reviews, except to reiterate FASTING IS NOT A FAD! 
“Shelly Sidhu” (October 2017, 5 stars) agreed:
This book is unbelievable. I work in the medical field and had no idea about a lot of this information. I am so much more informed and have applied this to my own life. I am buying copies for my NP friends that are in diabetes education. This sets the bar on a new way to treat patients. 
But “Anon for Now” (September 2017, 2 stars) said:
Believable information, but doesn’t offer a plan to make it usable. Also contradictory. He spends the first half of the book proving that calories are meaningless, then says not to eat during the day because you’ll get fat. What is the plan? Is it basically paleo + dairy, plus restricting calories? Waste of time and money. 
The Bottom Line: Is The Obesity Code Worth A Read?
Yes. This book has given a lot of people looking to lose weight a very different outlook on new ways to do so. The author specifically highlights diabetic and pre-diabetic people needing to drop a large amount of weight. There is no eating plan associated with this book, so those of you who are looking for a set-in-stone guide will not find it.
Intermittent fasting and losing your snacking habits will be some big life changes to make, but it’s worth a shot if you are struggling with dieting in general and want a fresh perspective on how to cut the pounds. Not everyone is able to fast for long periods without some detrimental effects (lightheadedness, fainting), so do please check with your health care provider before trying this.
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