The Obesity Code – by Jason Fung

Intermittent fasting is still an ongoing experiment in my life. Apart from Jason's bombastic writing style, I think this book is worth reading even if you decide not to do the fasting. In the second part, the book becomes dense with good nutrition information and facts—what to eat, why, how frequently and so on.


But all chronic diseases are multifactorial, and these factors are not mutually exclusive. They may all contribute to varying degrees.

There we have the real disease, and treatment must be directed against the ultimate, rather than the proximate cause.

Calories In – Calories Out = Body Fat If Calories Out remains stable over time, then reducing Calories In should produce weight loss. The First Law of Thermodynamics states that energy can neither be created nor destroyed in an isolated system. This law is often invoked to support the Calories In/Calories Out model.

But thermodynamics, a law of physics, has minimal relevance to human biology for the simple reason that the human body is not an isolated system. Energy is constantly entering and leaving. In fact, the very act we are most concerned about—eating—puts energy into the system. Food energy is also excreted from the system in the form of stool. Having studied a full year of thermodynamics in university, I can assure you that neither calories nor weight gain were mentioned even a single time.

Let’s take an analogy. Consider the money that you earn in a year (Money In) and the money that you spend (Money Out). Suppose you normally earn and also spend $100,000 per year. If Money In is now reduced to $25,000 per year, what would happen to Money Out? Would you continue to spend $100,000 per year? Probably you’re not so stupid, as you’d quickly become bankrupt.

Among the most consistent findings was the constant feeling of cold experienced by the participants.

[…] whether physical activity increases or decreases, it has virtually no relationship to the prevalence of obesity.

What happens to the excess fat that is produced through de novo lipogenesis? This newly synthesized fat can be stored as visceral fat (around organs), […]

Once we understand that obesity is a hormonal imbalance, we can begin to treat it. If we believe that excess calories cause obesity, then the treatment is to reduce calories. But this method has been a complete failure. However, if too much insulin causes obesity, then it becomes clear we need to lower insulin levels. The question is not how to balance calories; the question is how to balance our hormones. The most crucial question in obesity is how to reduce insulin.

The fat get fatter. The longer you are obese, the harder it is to eradicate. But you already knew that.

A long-standing obesity cycle is extremely difficult to break, and dietary changes alone may not be sufficient.

In a 2007 study that looked specifically at soft drinks, Dr. David Ludwig from Harvard University found that accepting funds from companies whose products are reviewed increased the likelihood of a favorable result by approximately 700 percent! This finding is echoed in the work of Marion Nestle, professor of nutrition and food studies at New York University. In 2001, she concluded that it is “difficult to find studies that did not come to conclusions favoring the sponsor’s commercial interest.”

Artificial sweeteners may also cause harm by increasing cravings. The brain may perceive an incomplete sense of reward by sensing sweetness without calories, which may then cause overcompensation and increased appetite and cravings.

Since artificial sweeteners also raise insulin levels, there is no benefit to using them. Eating chemicals that are not foods (such as aspartame, sucralose or acesulfam potassium) is not a good idea. They are synthesized in large chemical vats and added to foods because they happen to be sweet and not kill you.

There are no long-term data on the use of vinegar for weight loss. However, smaller short-term human studies suggest that vinegar may help reduce insulin resistance.

Two teaspoons of vinegar taken with a high-carbohydrate meal lowers blood sugar and insulin by as much as 34 percent, and taking it just before the meal was more effective than taking it five hours before meals.

Designed originally for diabetic patients, the index helped them make food choices. However, for the treatment of obesity, low–glycemic index diets have met with mixed success. Weight-reduction benefits have been elusive. And that’s because there is one particularly insurmountable problem with the glycemic index diet.

Blood glucose does not drive weight gain. But hormones—particularly insulin and cortisol—do.

Insulin can increase independently of blood sugar.

PROTEINS DIFFER GREATLY in their capacity to stimulate insulin,8 with dairy products in particular being potent stimuli.9 Dairy also shows the largest discrepancy between the blood glucose and insulin effect. It scores extremely low on the glycemic index (15 to 30), but very high on the insulin index (90 to 98). Milk does contain sugars, predominantly in the form of lactose. However, when tested, pure lactose has minimal effect on either the glycemic or insulin indexes.

Animal proteins tend to cause you to feel fuller for longer, with whey having the greatest effect.


ALMOST UBIQUITOUS IN refined and processed foods, sugar is not always labeled as such. Other names include sucrose, glucose, fructose, maltose, dextrose, molasses, hydrolyzed starch, honey, invert sugar, cane sugar, glucose-fructose, high fructose corn syrup, brown sugar, corn sweetener, rice/corn/cane/maple/malt/golden/palm syrup and agave nectar.

So what can you do about dessert? Follow the example of traditional societies. The best desserts are fresh seasonal fruits, preferably locally grown. A bowl of seasonal berries or cherries with whipped cream is a delicious way to end a meal. Alternatively, a small plate of nuts and cheeses also makes for a very satisfying end to a meal, without the burden of added sugars. Dark chocolate with more than 70 percent cacao, in moderation, is a surprisingly healthy treat.

Nuts, in moderation, are another good choice for an after-dinner indulgence. Most nuts are full of healthful monounsaturated fats, have little or no carbohydrates, and are also high in fiber, which increases their potential benefit.

A recent Spanish study found that adding 100 pistachios to one’s daily diet improved fasting glucose, insulin and insulin resistance.

Don’t replace sugar with artificial sweeteners, as they also raise insulin as much as sugar and are equally prone to causing obesity.

Just don’t snack

The greatest problem is that, like snacks, breakfast foods are often little more than dessert in disguise, […]

Whole oats and steel-cut oats are a good choice, requiring long cooking times because they contain significant amounts of fiber that requires heat and time to break down. Avoid instant oatmeal.

Eggs, previously shunned due to cholesterol concerns, can be enjoyed in a variety of ways: scrambled, over easy, sunny side up, hard-boiled, soft-boiled, poached, etc.

Beverages: No sugar added THE SUGAR-SWEETENED DRINK is one of the leading sources of added sugars. This includes all soda pop, sugar-sweetened teas, fruit juice, fruit punch, vitamin water, smoothies, shakes, lemonade, chocolate or flavored milk, iced coffee drinks and energy drinks.

However, moderate consumption of red wine does not raise insulin or impair insulin sensitivity, and therefore may be enjoyed.16 Up to two glasses a day is not associated with major weight gain17 and may improve insulin sensitivity.

Coffee: Healthier than we thought DUE TO ITS high caffeine content, coffee is sometimes considered unhealthy. However, recent research has come to the opposite conclusion,19 perhaps due to the fact that coffee is a major source of antioxidants,20 magnesium, lignans21 and chlorogenic acid.

You can use cinnamon, coconut oil, vanilla extract, almond extract and cream to flavor your coffee without changing its healthy nature. Avoid adding sugar or other sweeteners.

REFINED GRAINS SUCH as white flour stimulate insulin to a greater degree than virtually any other food. If you reduce your consumption of flour and refined grains, you will substantially improve your weight-loss potential. White flour, being nutritionally bankrupt, can be safely reduced or even eliminated from your diet. Enriched white flours have had all their nutrients stripped out during processing and later added back to retain a veneer of healthiness.

Avoid processed bakery foods that are mostly flour and other starches: bread, bagels, English muffins, roti, naan breads, dinner rolls, bread sticks, Melba toasts, crackers, tea biscuits, scones, tortillas, wraps, muffins, cookies, cakes, cupcakes and donuts.

Eggplant, kale, spinach, carrots, broccoli, peas, Brussels sprouts, tomatoes, asparagus, bell peppers, zucchini, cauliflower, avocados, lettuce, beets, cucumbers, watercress, cabbage, among others, are all extremely healthy carbohydrate-containing foods.

[…] protein cannot and should not be eliminated from your diet. (For more on protein, see chapter 17.) Instead, moderate the amount of protein in your diet to fall within 20 percent to 30 percent of your total calories.

Natural, unprocessed fats include olive oil, butter, coconut oil, beef tallow and leaf lard. The highly processed vegetable oils, high in inflammatory omega 6 fatty acids, may have some detrimental health effects.

Vinegar is also a protective factor. Used in many traditional foods, it may help reduce insulin spikes.

THERE ARE FIVE basic steps in weight loss: Reduce your consumption of added sugars. Reduced your consumption of refined grains. Moderate your protein intake. Increase your consumption of natural fats. Increase your consumption of fiber and vinegar.

Two major factors maintain our insulin at a high level. The first is the foods that we eat—which are what we usually change when we go on a diet. But we fail to address the other factor: the long-term problem of insulin resistance. This problem is one of meal timing.

To break the insulin-resistance cycle, we must have recurrent periods of very low insulin levels. (Remember that resistance depends on having both persistent and high levels.)

When we talk about fasting to break insulin resistance and lose weight, we are talking about intermittent fasts of twenty-four to thirty-six hours.

Regular fasting, by routinely lowering insulin levels, has been shown to significantly improve insulin sensitivity.8 This finding is the missing piece in the weight-loss puzzle.

Physicians have advocated fasting as far back as the mid 1800s.

So that answers the two unspoken questions. Is it unhealthy? The answer is no. Scientific studies conclude that fasting carries significant health benefits.

Some people prefer a daily sixteen-hour fast, which means that they eat all their meals within an eight-hour window.

Longer fasts are typically twenty-four to thirty-six hours, done two to three times per week. Prolonged fasting may range from one week to one month.

During a twenty-four-hour fast, you fast from dinner (or lunch or breakfast) the first day until dinner (or lunch or breakfast) the next day. Practically, this means missing breakfast, lunch and snacks on [… truncated due to giving out way too much of the book]

During a thirty-six-hour fast, you fast from dinner on the first day until breakfast two days later. This means missing breakfast, lunch, dinner and snacks for one entire day. You would be skipping three meals as you fast from 7:00 p.m. the first day to 7:00 a.m. two days later.

Longer fasting periods produce lower insulin levels, greater weight loss and greater blood sugar reduction in diabetics. In the Intensive Dietary Management Clinic, we will typically use a twenty-four-hour or thirty-six-hour fast two to three times per week. For severe diabetes, patients may fast for one to two weeks, but only under close medical supervision. You may take a general multivitamin if you’re concerned about micronutrient deficiency.

ALL CALORIE-CONTAINING FOODS and beverages are withheld during fasting. However, you must stay well hydrated throughout your fast. Water, both still and sparkling, is always a good choice. Aim to drink two liters of water daily. As a good practice, start every day with eight ounces of cool water to ensure adequate hydration as the day begins.

Adding a squeeze of lemon or lime flavors the water. Alternatively, you can add some slices of orange or cucumber to a pitcher of water for an infusion of flavor, and then enjoy the water throughout the day. You can dilute apple-cider vinegar in water and then drink it, which may help with your blood sugars.

All types of tea are excellent, including green, black, oolong and herbal.

You can use spices such as cinnamon or nutmeg to add flavor to your tea.

Coffee, caffeinated or decaffeinated, is also permitted.

Homemade bone broth, made from beef, pork, chicken or fish bones, is a good choice for fasting days.

Be careful to break your fast gently. Overeating right after fasting may lead to stomach discomfort.

Staying busy during a fast day is often helpful. Fasting during a busy day at work keeps your mind off eating.

I get dizzy when I fast. What can I do? MOST LIKELY, YOU’RE becoming dehydrated. Preventing this requires both salt and water. Be sure to drink plenty of fluids. However, the low salt intake on fasting days may cause some dizziness. Extra sea salt in broth or mineral water often helps alleviate the dizziness. Another possibility is that your blood pressure is too low—particularly if you’re taking medications for hypertension. Speak to your physician about adjusting your medications.

I get headaches when I fast. What can I do? AS ABOVE, TRY increasing your salt intake. Headaches are quite common the first few times you try a fast. It is believed that they’re caused by the transition from a relatively high-salt diet to very low salt intake on fasting days.

Don’t tell everybody you are fasting: Most people will try to discourage you, as they do not understand the benefits. A close-knit support group is beneficial, but telling everybody you know is not a good idea.