My single best weight-loss tip

Weight scale with a measuring tape. Concept- lifestyle, sports and diet for weight loss. Copy space. On the measuring scale written word - HELP!

Just following up on our post from last week – Robert – I wanted to share with you my single best weight-loss tip.

In your body, nothing happens by accident. Every single physiologic process is a tight orchestration of hormonal signals. Whether our heart beats faster or slower is tightly controlled by hormones. Whether we urinate a lot or a little is tightly controlled by hormones. Whether the calories we eat are burned as energy or stored as body fat is also tightly controlled by hormones. So, the main problem of obesity is not necessarily the calories we eat, but how they are spent. And the main hormone we need to know about is insulin.

Insulin is a fat-storing hormone. There’s nothing wrong with that – that is simply its job. When we eat, insulin goes up, signaling the body to store some food energy as body fat. When we don’t eat, then insulin goes down, signaling the body to burn this stored energy (body fat). Higher than usual insulin levels tell our body to store more food energy as body fat.

Hormones are central to obesity as is everything about human metabolism, including body weight. A critical physiological variable such as body fatness is not left up to only the vagaries of daily caloric intake and exercise. If early humans were too fat, they could not easily run and catch prey and would be more easily caught themselves. If they were too skinny, they would not be able to survive the lean times. Body fatness is a critical determinant of species survival.


As such, we rely on hormones to precisely and tightly regulate body fat. We don’t consciously control our body weight any more than we control our heart rates or our body temperatures. These are automatically regulated, and so is our weight. Hormones tell us we are hungry (ghrelin). Hormones tell us we are full (peptide YY, cholecystokinin). Hormones increase energy expenditure (adrenalin). Hormones shut down energy expenditure (thyroid hormone). Obesity is a hormonal dysregulation of fat accumulation. We get fat because we’ve given our body the hormonal signal to gain body fat. And those hormonal signals go up or down according to our diet.

Obesity is a hormonal, not a caloric imbalance.

Insulin levels are almost 20 percent higher in obese subjects, and these elevated levels are strongly correlated to important indices such as waist circumference and waist/hip ratio. Does high insulin cause obesity?

The “insulin causes obesity” hypothesis is easily tested. If you give insulin to a random group of people, will they gain fat? The short answer is an emphatic “Yes!” Patients who use insulin regularly and physicians who prescribe it already know the awful truth: the more insulin you give, the more obesity you get. Numerous studies have already demonstrated this fact. Insulin causes weight gain.

In the landmark 1993 Diabetes Control and Complications Trial, researchers compared a standard dose of insulin to a high dose designed to tightly control blood sugars in type 1 diabetic patients. Large insulin doses controlled blood sugars better, but what happened to their weight? Participants in the high-dose group gained, on average, approximately 9.8 pounds (4.5 kilograms) more than participants in the standard group. More than 30 percent of patients experienced “major” weight gain!

Prior to the study, both groups were more or less equal in weight, with little obesity. The only difference between the groups was the amount of insulin administered. Insulin levels were increased. Patients gained weight. Insulin causes obesity. As insulin goes up, one effect is that the body set weight goes up. The hypothalamus sends out hormonal signals to the body to gain weight and we become hungry and eat. If we deliberately restrict caloric intake, then our total energy expenditure will decrease. The result may still be the same – weight gain.


Once we understand that obesity is a hormonal imbalance, we can begin to treat it. If we believe that excess calories alone cause obesity, then the treatment is to reduce calories. But this method has been a long-term failure. However, if too much insulin causes obesity, then it becomes clear that we need to lower insulin levels.

The question is not how to balance calories; the question is how to balance our hormones especially insulin. There are really only two ways that insulin increases. Either:

  1. We eat more foods that stimulate insulin
  2. We eat the same insulin-stimulating foods, but more frequently.

My book, The Obesity Code laid out the science behind weight gain and how to apply that knowledge to lose weight. It forms the theory behind the IDM program’s many successes over these many years. This book’s goal is to embrace these ideas and make it easier to implement in day to day life.


My key to long lasting weight control is to control the main hormone responsible, which is insulin. There are no drugs that can control insulin. Controlling insulin requires a change in our diet, which is composed of two factors – how high the insulin levels are after meals, and how long they persist. This boils down to two simple factors:

  1. What we eat – determines how high insulin spikes
  2. When we eat – determines how persistent insulin is

Most diets concern themselves with only the first question and therefore fail over the long term. It is not possible to address only half the problem and expect success.

In terms of the foods, this is not a low-calorie diet. This is not even necessarily a low-carbohydrate diet. This is not a vegetarian diet. This is not a low-fat diet. This is not a carnivore diet. This is a diet designed to lower insulin levels because insulin is the physiologic trigger of fat storage. If you want to lower fat storage, you need to lower insulin, and this may be done even with a high-carbohydrate diet.

Many traditional societies have eaten carbohydrate-based diets without suffering from rampant obesity. In the 1970s, before the obesity epidemic, the Irish were loving their potatoes. The Asians were loving their white rice. The French were loving their bread.

Even in America, let’s remember the 1970s. Disco was sweeping the nation. Star Wars and Jaws played to packed theatres. If you looked at an old photograph from that era, perhaps you might be amazed at several things. First, why anybody ever thought bell bottoms were cool. Second, it’s amazing just how little obesity there is. Take a look at some old high school yearbooks from the 1970s. There is virtually no obesity. Perhaps one child in a hundred.

What was the diet of the 1970s? They were eating white bread and jam. They were eating ice cream. They were eating Oreo cookies. There were not eating whole-wheat pasta. They were not eating quinoa. They were not eating kale. They were not counting calories. They were not counting net carbs. They were not even really exercising much. These people were doing everything ‘wrong’ yet, seemingly effortlessly, there was no obesity. Why?

What about the diet of the Chinese in the 1980s? They were eating tons of white rice. On average, over 300 grams per day, compared to a low carb diet of less than 50 grams and all highly refined. Yet they had virtually no obesity. Why?

What about the diet of the Okinawan? Over 80% carbohydrates, and mostly sweet potato, which has some sugar in it. What about the Irish in the 1970s, with their beloved beer and potatoes? They didn’t think twice about what they were eating, but until recently there was almost no obesity. Why?

The answer is simple. Come closer. Listen carefully.


They were not eating all the time.

When you don’t eat, this is technically known as ‘fasting’. This is the reason there is the English word ‘break fast’ or breakfast, the meal that breaks your fast. During your sleep, you are (presumably) not eating and therefore fasting. This allows time for your body to digest the foods, process the nutrients and burn the rest for energy to power your vital organs and muscles. In order to maintain a stable weight, you must balance feeding and fasting.

During feeding, you store food energy as body fat. During fasting, you burn body fat for energy. If you balance those two, your weight will remain stable. If you are predominantly feeding, you will gain weight. If you are predominantly fasting, you will lose weight. So, here’s my best single tip for weight loss. It’s so simple and obvious that even a 5-year old could have come up with it.

Don’t eat all the time.

Unfortunately, most nutritional authorities tell you the exact opposite. Eat six times a day. Eat lots of snacks. Eat before you go to bed. Eat, eat, eat – even to lose weight! It sounds backwards because it is backwards. Instead, it may be better to use intermittent fasting, a dietary technique used successfully for countless generations.

Also, check out the free Facebook support group – The Obesity Code Network for fasting support and education.

Dr. Jason Fung

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Dr. Fung’s top posts

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  1. Zoe
    Dr. Fung - you are so right! We are a culture that is constantly bombarded with food, food, food.
    Everywhere I go people are eating, A trip to see a movie- the lines are long - not to get tickets but to get more food and I’m not just talking about popcorn! I’m always amazed as I think “ but haven’t you just come from home - why are you eating now? Ditto for my first ball game in the early 90’s. As soon as people had seats they were up and moving. In my naivety I thought they were going to the bathroom!!
    But they all came back laden with food!! Interesting too, growing up in England in the 50’s and 60’s if people were overweight ( and never to the extent of the present obesity epidemic), it was often put down to “ its their glands.” It seems that never was a more true word spoken. Today’s epidemic of morbid obesity with ALL of its ensuing health issues, is the reason I quit my nursing career after 46 years. It was too depressing. Despite all the great medical advances, we are sicker than we’ve ever been. We really are a culture dying to eat!
    Keep up the great work!
  2. Joe
    Preach Dr Fung preach! Great article. Meal timing is of absolute importance. I start the day with a black coffee and just see what happens. Sometimes the first meal is at 1pm, sometimes 3pm. It just depends on how I feel. I try to listen to my body’s signals and even if hunger does develop, sometimes I like to push through it and lengthen my fast.

    This site is too obsessed with keto this and keto that! Stick to 20g of carbs or 50g of carbs! Who wants to eat in such a scientific way where every single thing is measured and weighed! Meal timing, intermittent fasting, longer fasts....these are the keys to healing the gut....I would say more so that just dedicating your life to a rigid diet.

    The truth is that human metabolism is so complex that we are probably not even scratching the surface when it comes to understanding how we digest different foods. But one thing we can agree on (as Dr Fungs article clearly states) is that we cannot eat all the time. The digestive system needs a break from food to help it digest food thoroughly , repair, heal, rejuvenate etc.

    Fasting is the cure! But in modern day society....with the junk food industry pushing its snacks, food availability, supermarkets on every street corner etc etc....fasting is seen to be some sort of weird dangerous practice!

  3. Charlotte
    Makes so much sense. I'm getting ready to order " The Obesity code now".
  4. Jude
    Don't forget about the possible effects of endocrine disrupting chemicals accumulating since the 1970's as an additional explanation to frequency of food intake.
  5. Don
    We like to think that fiber is protective but there are many kinds of ‘fiber’ so way to broad to say it is protective. I understand that it is a simplified epidemiological diagram though.
  6. Don
    What about glucagon secretion and signalling? I can appreciate that high insulin triggers fat storage but that is not the only part. It’s also not just the pancreas but liver function as well. If you are not talking about both then you are only looking at 1/2 the problem.
  7. Geoff
    So you are disregarding the effects of carbohydrate / protein / fat intake??

    Hormonal imbalance of course.

    Argument presented falls down after that because of the one way street that is prescribed.

    Unfortunately balancing carbohydrate / protein / fat intake (very well demonstrated by cases described on this website) tends also to describe a one way street. (although the most effective proven method, and many individuals appear to be able to stick to this one way street)

    About time someone (on this website) added the obvious effects of modern lifestyle (chasing a living?), obvious stress patterns that result and how these effect hormonal imbalance.

    Fascinating subject - much to learn, we just shouldn't get stuck in our 'eureka' moments hailing them as complete solutions.

  8. Poppy
    This article is very long-winded, what is the weight loss tip please?
    Replies: #18, #33, #43
  9. 2 comments removed
  10. Mark Foura
    A little disappointed in the final analysis and lack of direct information.
    Your article states:
    1. What we eat – determines how high insulin spikes
    2. When we eat – determines how persistent insulin is
    Don’t eat all the time.
    There is no direction on when to actually eat, to address lowering the insulin levels.

    I am a type two diabetic with a titanium mitral valve and definitely need to lose some weight.

    What is the best time of day for me to eat to interrupt the insulin persistability, as per point number two??
    ie: main meal at lunch,? or dinner, skip brekky to continue sleep fast???
    Cheers, Mark.

    Replies: #19, #52
  11. Wendy
    I started doing the 16:8 fasting. Lost no weight, actually put a little on, and lost my period. I also started having fits of depression and anxiety attacks.

    I started breakfast again and I have my period back and my moods are slowly recovering.

    I see and read so much about the benefits of fasting and can’t help but feel sad and frustrated that my body doesn’t react well to it.

    Replies: #31, #47
  12. trevor costigan
    i dont read never have ,books i mean , but with old age problems and all the ill health,that comes with it.
    it was time, so i picked up your book and read it twice to make sure i got the program.
    by following the fasting code . i lost 10 kg in 60 days.
    anyone can do it, and to think we sleep through the first 12 hours of the fast.
    how simple was that.
    thank you
    mr t c perth australia
  13. Lorna
    You say we need to stop eating all the time as in the 70s people were eating carb laden meals and not putting on weight - I never heard that anyone was fasting in the 70s, in fact from memory meal times were adhered to- 3 definite meals a day and often including morning and afternoon tea, I would say though, that portion sizes were smaller in the 70s than now
    Replies: #15, #46
  14. Cassie
    Yes! We rarely had a snack and the biggest thing I remember is we never ate after dinner. No snacking in front of the television all night long. Our meals were also so much smaller than what they are today. I remember breakfast might have been toast and jam or a small bowl of cereal but that was it. Lunch was chicken salad perhaps with a piece of fruit. Dinner was a small piece of meat, if we had any that night, with a salad or soup and usually another vegetable. Fresh fruit for dessert or maybe shortcake or angel food cake with the fruit. After dinner, we were done eating until the next morning.
  15. SM
    In the 70's and 80's, we were eating breakfast, lunch and supper with cheese and crackers at recess, 4 slices of peanut butter bread after school and a snack before bed. That's six meals and, in a class of 38 kids, I remember only 1 obese child. The difference had nothing to do with food or fasting. It was how much we played and ran around. We were always playing...tag, ball, hide and seek, hopscotch, floor hockey, soccer, skipping, ball. That, I suspect, was a significant factor with being able to eat whatever we wanted and be the thinnest kids in school. Everyone these days is looking at what we eat, don't eat and the number of meals in a day. The bigger picture is that many people-myself included-spend more time sitting. Adults and children need more play time.
    Reply: #22
  16. 1 comment removed
  17. Kristin Parker Team Diet Doctor

    This article is very long-winded, what is the weight loss tip please?

    Controlling insulin by controlling what we eat and/or when we eat.

  18. Kristin Parker Team Diet Doctor
    Mark, here is good information about fasting and the different fasting protocols.


  19. Kazzy
    Umm, looking at the graphic, what is the "vinegar" for?
  20. Stephanie
    Adding vinegar to food has been shown to lower the glycaemic index of that food, and hence to also lower the insulin response.
  21. Stephanie
    Yes, also exercise makes our cells more insulin-sensitive, leading to lower levels of circulating insulin.
  22. M. Sajid
    Dr. Fung, Thank you for your tip and advice, but I want to clear a question in my mind that why in type 2 diabetes weight loss occurs even with high insulin levels in body? Please guide!
    Replies: #25, #53
  23. Pam
    I have been doing keto since May 2017 with good necessary weight loss, maintained ever since. I suppose I fast from around 7pm until 9am or thereabouts but can't miss meals during the day without losing energy. From time to time, I have increased my carbohydrates with chocolate and pastries and the occasional piece of bread so to the point of this message - it doesn't take many of these "treats" to make me ravenously hungry before my next meal and bloated and uncomfortable so beware falling back into old habits because good health comes with control - proof is in the eating. Happy healthy for the first time in years so stick with it!
  24. Kristin Parker Team Diet Doctor

    Dr. Fung, Thank you for your tip and advice, but I want to clear a question in my mind that why in type 2 diabetes weight loss occurs even with high insulin levels in body? Please guide!

    Ideally when eating very low carb and incorporating fasting, that insulin level will go down. That's what unlocks the fat loss.


  25. 1 comment removed
  26. Kazzy
    I’m wondering, along with M. Saiid, why weight loss occurs with high insulin? After all, unexplained weight loss is a symptom of undiscovered diabetes, is it not?
    Reply: #28
  27. Exona
    kazzy, Unexplained weight loss is a symptom of type one, not type two diabetes.
    Reply: #29
  28. Exona
    Never mind, I see team diet doctors response. I guess I don’t know what I’m talking about! :-)
  29. MIRIAM
    Since I read this post a few days ago, I too have been trying to puzzle it out. I remember what people ate in the 1970s and 80s and I never heard of anyone fasting then apart from for religious reasons. Unless my memory fails me, the diet industry was well under-way by the 1960s. Anyone else remember 'Nimble' bread? There were nowhere near as many obese people, obviously, but there was a a great deal of overweight. Most people ate between meals and Dr Fung is right - wholemeal alternatives were relatively unknown and kale was fed to cattle! My parents (both fat) always ate a sandwich before bed as supper was eaten at 5pm. There was always a home-made cake on the go in our house.

    I thought that Jason Fung was a devotee of LCHF but it seems now that, for him, fasting is paramount. I can attest to the power of fasting as I'm a 65-year-old female who lost about 60 lbs in 6 months 4 years ago following the 5:2 diet. Along with my vegetarian husband, I 'progressed' to a moderate low-carbohydrate diet and slowly regained nearly 40 lbs so we began 5:2 again in late July with already excellent results. At the same time, I reduced the amount of dairy and fat we eat, especially double cream, which I think is helping, so its a 'MCMF' diet + 5:2 which works for us, at least at the moment.

    We are both very happy to exclude bread, pasta, rice, cakes, biscuits, pastry etc from our diet and no sugar. Our main carbohydrate sources are pulses (I usually eat meat or fish instead) and carrots, swede etc, an occasional small serving of quinoa plus whatever carbohydrate is in the other veg we eat so much of. We both feel we've never eaten so well or enjoyed our food more. (We also both like red wine but 5:2 has helped to curb that!)

    Is Dr Fung really recommending that we eat Oreos and white rice as long as we never eat breakfast or between meals? That seems to be the take-home message of his post (I hope I'm wrong!) Sorry to appear flippant but I genuinely do not understand what his 'core message' is now.

    Reply: #35
  30. Sylvie
    So sorry to hear this, Wendy.

    The opposite happened to me and some of my friend who did the 16:8 fasting. Might be a good idea to read DrFung book on fasting. There are dos and don’ts To respect, and when we start this, will feel a bit rough in the first week or two, but things do improve. Now 50 yrs old and my skin cleared -had acne all my life. I have more energy and mental clarity.

    Don’t give up!

  31. Suzanne
    I have Type 1 diabetes. I administer my own insulin. How can I manage this?? Until this diagnosis i never weighed more than 100 lbs!! Now the scales just keep going up and up! Help!!
    Replies: #39, #41
  32. Barbara R.
    It boils down to, "Don't eat all the time". We eat too often and too late in the evening. This comes back
    to the idea of fasting at least overnight to give the body a rest from digestion so it can
    turn it's attention to repairing itself without that burden... break-fast = breakfast.
  33. 1 comment removed
  34. Kristin Parker Team Diet Doctor
    Miriam, the core message is that when we eat plays more of a role in weight loss than previously though. No, eating oreos is not healthy ;) The best meals for eating windows is keto/low carb to help normalize blood sugar and insulin.
  35. MIRIAM
    Thanks Kristin. I hope my (overlong) post made clear that I'm signed up to both IF and low-ish carbohydrate eating (my veggie husband notwithstanding). 'Certainly no oreos in our house!

    Unfortunately, I think Dr Fung's article risks confusing people. His comments about people's diets and frequency of eating in certain cultures and in the 1970s are too generalised to be very meaningful and it's as if, for him, only the timing of meals really matters. As you say, keto/low carb will be much more effective and healthful than a diet full of refined carbohydrate and starch even if you're doing IF. And I think that applies however small your eating window!

    I may have got it all wrong but, from what he writes above and elsewhere, Dr Fung doesn't seem to think LCHF/keto is the only (or even best) option for health and weight-loss. And by the way, having just acquired and read Zoe Harcombe's 2014 book ' The Harcombe Diet' it seems, unless she has subsquently revised it, neither does she!

  36. Lorena
    I agree that the article might confuse people. About a year ago, I stumbled across Dr. Fung on YouTube, started watching his videos, bought his book, and then stumbled onto Dietdoctor, so I know what Dr. Fung has researched, what he's found, and what he thinks about IF and low-carbohydrate. It made the article an easy read for me, and not at all confusing. But for those of you who aren't familiar:

    Basically, he's saying that the primary key is to stop eating all the time. Stop snacking, and don't eat too early/too late in the day. The second thing he's saying is to stop eating foods that really elevate our insulin (in other words, stop eating high-sugar foods). It doesn't necessarily equate to low-carb, but it does mean we need to reduce processed/refined foods and high-sugar foods.

    When I read his book, I thought, "I can do that -- I can eliminate snacks." I am pre-menopausal and was stuck despite eating moderately low-carb, I had stopped losing weight for about 7 months. I cut out snacks and didn't worry about eating slightly more at mealtimes because I felt a bit hungrier at first -- I just didn't eat more starchy, sugary foods at my meals ... and I lost 5 pounds in one week. I continued to lose, and am now down 21 pounds in about 5 months, but not just from cutting out snacks. I also pushed my breakfast to later in the day (to 9 am at the earliest), and I got a bit stricter with the carbs (but I still eat about 30-40 grams a day). I did one thing at a time ... first, cut out snacks. Then I started eating breakfast 30 minutes later than usual, then another 30, and then 2 hours later (I used to have breakfast at 6:30; so now I wait an additional 2.5 hours). It's relatively painless, and I managed to keep losing, albeit more slowly, over the holidays. Hope this helps!

  37. 1 comment removed
  38. Anastasia
    I’m also interested in how type 1diabegics manage insulin and A1C without gaining weight!
  39. Emball6
    Great article.

    However, I don’t believe you can fit everyone in to this box of ‘eating less will help you lose weight’. Yes, we are bombarded with food in our daily lives. But when I (personally) eat less or fast,I actually stall any loss and will often gain weight.

    I guess we are all different. Interesting article nonetheless.

  40. Stephanie
    Hi Suzanne, I have type one, and have been eating low-carb/keto for 9 months and also intermittent fasting. I finish the evening meal at 7 pm, and eat the next day anytime I'm hungry AFTER 11 am, hence 16/8. and have never felt better. My blood glucose levels were erratic and I was having hypo's just about every day. Now I am on half the insulin I was on, and have a hypo about once a month. I am also post-menopausal and not very active due to other issues, so weight loss is happening but very slowly. Younger fitter people should lose quicker. My nephew is also T1 and he is losing loads of weight with this approach he has reduced his doses to about a third of what he was taking.
    The issue with type one is the old advice that we need to eat all the time, carb