Lights off for weight loss

I have often said that weight loss is a lot more complicated than simply “eating less and exercising more”. New research indicates how much more complicated weight gain is due to circadian rhythms. Our brain and virtually all of our cells are programmed to run on a 24-hour cycle to help us optimize future events (like sleep and eating) that are essential for life. In fact, even fungi have these biological clocks. There is a central clock in the brain that responds to light and dark by releasing the hormone melatonin. Melatonin, as well as other hormones, prepares the individual cells in different organs for an anticipated stimulus that allows those organs to rapidly respond with the greatest efficiency. The adipose tissue is one of those organs. This is why the uptake and release of fatty acids by the adipose tissue has a strong circadian rhythm (1). One hormone that is exclusively released by the fat cells is leptin. Both leptin and ghrelin (the hunger hormone released from the gut) are also under circadian control (2).

The bottom line is that as our light/dark cycles are becoming more distorted, the hormones that affect our appetite are also being adversely affected. It is known that sleep-deprived individuals are more inflamed (3) as well as have abnormalities in glucose metabolism (4).

New research indicates that increased light during the normal sleeping cycle for mice increases their weight and their fat mass (5). Most disturbing is that you only need a very dim light on during their normal sleep cycle to increase weight gain in the animals. The more intense the light during their normal sleep cycle, the greater the weight gain.

This is also true for humans, as discussed in an online pre-publication release that will be published in the March 2011 issue of the Journal of Endocrinology and Metabolism (6). In this study, subjects were exposed to dim lighting (about one-half the intensity of a typical office light) for eight hours prior to bedtime; then the release of melatonin would be completely suppressed for about 90 minutes after they started sleeping. Just like the mice, if the light was on, even dimly, while they were sleeping, their melatonin levels were depressed by about 50 percent. The less melatonin you release during sleep, the more body fat you accumulate.

This leads to an interesting thought. It is known that increased television viewing and prolonged computer use leads to increased weight gain. It has always been assumed that this was because the person was not exercising. This new data strongly suggests it is not a lack of physical activity that is the problem, but the disturbances in circadian rhythms that may be the underlying problem. It’s hard to exercise in the dark, but you sure can sleep better and get thinner in the process if you keep the lights off.


1. Bray MS and Young ME. “Circadian rhythms in the development of obesity: potential role for the circadian clock within the adipocyte.” Obesity Rev 8: 169-181 (2006)

2. Karla SP, Bagnasco M, Otukonyong EE, Dube MG, and Kalra PS. Rhythmic, reciprocal ghrelin and leptin signaling: new insight in the development of obesity.” Regulatory Peptides 111: 1-11 (2003)

3. Vgontzas AN, Papanicolaou DA, Bixler EO, Kales A, Tyson K, and Chrousos GP. “Elevation of plasma cytokines in disorders of excessive daytime sleepiness.” J Clin Endocrinol Metab 82: 1313-1316 (1997)

4. Spiegel K, Leproult R, and Van Cauter E. “Impact of sleep debt on metabolic and endocrine function.” Lancet 354: 1435-1439 (1999)

5. Fonken LK, Workman, JL, Walton JC, Weil ZM, Morris JS, Haim A, and Nelson RJ. “Light at night increases body mass by shifting the time of food intake.” Proc Natl Acad Sci USA 107: 18664-18669 (2010)

6. Gooley JJ, Chamberlain K, Smith KA, Shalsa SBS, Rajaatnam SMW, van Reen E, Zeitzer JM, Czeisler CA, and Lockley SW. “Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.” J Clin Endocrino Metabol doi:10.1210/jc.2010-2098

Nothing contained in this blog is intended to be instructional for medial diagnosis or treatment. If you have a medical concern or issue, please consult your personal physician immediately.

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About Dr. Barry Sears

Dr. Barry Sears is a leading authority on the impact of the diet on hormonal response, genetic expression, and inflammation. A former research scientist at the Boston University School of Medicine and the Massachusetts Institute of Technology, Dr. Sears has dedicated his research efforts over the past 30 years to the study of lipids. He has published more than 30 scientific articles and holds 13 U.S. patents in the areas of intravenous drug delivery systems and hormonal regulation for the treatment of cardiovascular disease. He has also written 13 books, including the New York Times #1 best-seller "The Zone". These books have sold more than 5 million copies in the U.S. and have been translated into 22 different languages.

74 thoughts on “Lights off for weight loss

  1. Very few times I have taken melatonin (time release, usually 3mg) at night, I woke up in the morning with a strange sensation, like a mild headache or dizziness

  2. This is very interesting. I noticed when I started working full-time after college, I started to gain weight due to being in front of the computer for 8+ hours. After being on the zone as well as exercising 5+ times during the week, I’ve managed to lose the weight I’ve gained.

    Thank you Barry! :)

  3. I am currently going through menapause, I am misserable most of the time but nights are worse. I have gained 20 pounds in 6 months, mostly in the mid section. What do you recommend?

    • As one goes through menopause, insulin levels begin to raise as estrogen levels drop. This is the primary reason you are gaining the excess weight. My recommendation would be a strict Zone Diet that that will help control the rising insulin levels especially when coupled with supplemental fish oil to help re-establish better hormonal communication by the reduction of cellular inflammation.

      • As a nutritionist & health educator. I recommend your hormones be
        tested and you start using bioidental hormones. When estrogen is low
        coritsol rises, that is why you wake up at night. Sleep deprivation & low
        hormones cause weight gain.

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  5. I am on bio-identical hormone replacement therapy. Taking estrogen, progestron,and testetrone. Also DHEA, Vit D3, Nature Thryiod, Synthroid, and multivitamin. I am considering a fish oil supplement. I have puffy eyes and feel swollen hands and feet every morning. I eat healthy using the Weight Watchers guidelines. I weigh 130 and I’m 5 ft 2 inches. 54 years old. Help I don’t feel good. I exercise regularly including strength training and aerobic exercise.

    • Hi Patty

      Why not stop Weight Watchers for 2 weeks and try the Zone and see if there is any difference – I am sure there will be a big improvement. I heard that with the new WW points they are saying you can have fruit on its own all day long. I know if I did that I would be sick – too much sugar. I dont know what they were thinking when they introduced that part of it to the guidelines.

      Definitely start taking the fish oil.

    • Patty,
      You can try watching how much sugar and salt you get, even in the form of diet sodas. When women go through menopause they become more salt sensitive and so they will tend to overreact with bloating a cardiologist said to me. And it looks like from Dr. Sears women are more sugar sensitive because the insulin levels elevate as estrogen declines.
      A good diet of meat,veggies,fish, good dairy and butter helped my bones and hormones tremendously. You can do almost anything with a good homemade yogurt for a treat (it is low GI). A daily slice of sour dough bread is ok because it has a lower GI then white and whole grain bread according to the Cereal Institute. I use some melatonin at night to sleep and I sleep very well now, but I have tried cutting out tv at night and my computer work a few hours before sleep, and that works great too. My bones are good now and I feel good. I am on a small dose of hormone replacement too. Hormones didn’t do the job all by themselves, I had to change my bad habits.

    • I recommend adding some B-Complex and B-6 to your vitamin regimen. Also remove gluten from your diet could be causing swelling.

  6. Just wondering how to help my body get through working 12 hour night shifts. Im new to the Zone program and I do supplement with Melatonin before sleep, what else could help?

    • I would suggest extra fish oil to further reduce any cellular inflammation in the brain. We did an interesting pilot study with medical residents subjected to a two-week period of sleep only 4 hours per night due to their medical rotation schedule. Half of the residents were delivered Zone meals and took 5 grams of EPA and DHA per day. The other half were on their own. After two weeks, those medical residents on the Zone program had lose excess body fat, had less cellular inflammation, and no loss of cognitive function. The other residents gained fat and were operating at the cognitive level of an 85-old individual. Although the stress was the same for both groups, their ability to handle that stress was dramatically altered by the diet.

    • It will ultimately depend on their levels of cellular inflammation that causes insulin resistance. Unfortuantely, the levels of cellular inflammation are going up in every segment of the U.S. population because of the saturation of our diets with refined carbohydrates and cheap vegetable oils rich in omega-6 fatty acids.

  7. Hi Dr. Sears -I am on the Zone and having great success with it. – Re: lighting and sleep, I’m wondering how ‘dim’ is dim enough. I leave on a large Himalayan rock salt lamp (the pink ones) at night, as a nightlight — they take one 4-7watt bulb; would that have a negative effect, do you think? If so, would wearing a sleep mask do the trick to eliminate it? Secondly, do you think that taking OTC liquid melatonin (from health food stores) at night is advisable or beneficial? Thank you.

  8. All good stuff- I’m a Zoner myself and love it! How do you count your daily fish oil supplement into your menu- as a fat…..but how much – considering I’m a 3 block woman!!
    love to know!

  9. Ok, less light in the winter time before bed time.
    Now what about summer time when the sun doesn’t set until 9 PM?? Too much light before bed time eh???
    Would appreciate a response.

      • Thanks for your reply Dr. Sears.
        Maybe this is odd, but in the summer staying outside till sunset (without shades) doesn’t affect my sleep adversely. Actually, by far I get my best sleep in the summer months. Seems the more daylight I get the better I sleep. My doctors have pondered this.

      • Hi Dr Sears

        I have been wanting to ask this question for a long time. 8 hours of sleep seems to be the perfect number that we should aim for but I read if you follow the Zone correctly you actually dont need as much sleep. This is because your body is functioning at its best. I try to get to bed earlier but when I do get into bed it takes me ages to sleep … I process the day and then think about all the things for the next day!

        Is there any news on when the forum will be back? It has been 4 months now without it.

  10. I am a 46 year old woman who exercises vigorously with cardio and weight training at least 5 times a week. I also follow a zone diet, but I do cheat on the weekends. Over the last year, my metabolism has come to a stand still. I now have a “gut” which I never ever had my entire life. I am 5’1″ tall or short, and I weighed between 120-125 up until this last year, where I gained 10 pounds. I think some of it is muscle weight, as I am still a size 4-6 in pants, but now my gut hangs over my pants. I am miserable, but cannot seem to get this off no matter what I do. Help!!!!!!!!!!!!!!

    • It is likely that you are entering into peri-menopause in which estrogen levels are beginning to drop. The result is a corresponding rise in insulin levels that is driving the fat accumulation. I would suggest following a more strict Zone diet (using primarily vegetables as your carbohydrates) every day for 30 days. If you begin to see a significant reduction in body fat, then you know this will be your dietary prescription for the rest of your life.

  11. I am a mom of 9 with about 60 lbs to lose. We drink raw milk in our family and eats lots of fresh veggies and fruit. We obviously have a very tight budget with so many of us. I am still breastfeeding my youngest who just turned one. I have looked over the Zone but don’t see how I can afford all the Zone products. I would love any help you can offer. Thanks!!!

    • Wow – 9! I thought I had a large family at 7! There is no way that I can afford the Zone products either, even when they have items on sale. It just costs too much. I am normally the only Zone eater in my family (although the kids do have a Zone bar from time to time), but try to give them a healthy meal that I can modify for myself to stay on the Zone. For instance, tonight I made chicken fajitas, but I didn’t use a tortilla and just had chicken, black beans, chopped tomatoes, and sauteed peppers & onions. Another night I made chicken w/shake n bake, a salad, rice. I ate the chicken, a tiny bit of rice, and a good amount of salad. Hope that helps! -Jen

    • Hi Nancy,

      I am of quite modest means (but have no children) and manage the zone rules with (believe it or not) pretty much sardines, apples/oranges, olive oil, and coffee with coffeemate – for about $3 a day.

      I suggest for protein you use Turkey, chicken, sardines (15 oz. cans with tomato sauce), canned salmon, canned mackerel (if you can stand it) or lentils (they have a good protein/carb balance); forget the milk, keep on with the fruit and vegetables, and use the zone “blocks” rules. The fish I mentioned have lots of omega 3 (important you get alot for the baby too!) and vitamin D, and are relatively cheap. Hope that helps.

    • You only have to make a few adjustments in your current diet. The first is making sure you are getting adequate protein at each meal. The most inexpensive source of high-quality protein is egg whites (the yolks are rich in arachidonic acid). I would also consider eating more vegetables, and less fruits, and essentially cut out grains and starches. The most valuable supplement Zone supplement is our purified fish oil. The diet can be done on your own as outlined above.

  12. I love the zone, but have a terrible time with breakfast because I don’t eat eggs or cottage cheese (a texture thing that I have never been able to stomach) and find the only thing I can stomach in the morning is the steel cut oatmeal and turkey bacon. I have eaten this for over 8 years now every morning and it absolutely makes me gag now. Can you offer some bean/toco type alterrnatives or something else so I can get going and stay on track. This really is a problem for me. Many thanks, Nancy

    • How about yogurt? Chobani is pretty close to being Zone balanced – you just need to add the fat (I use natural peanut butter or peanuts to balance out the blocks). It is a normal breakfast item for me, and they have many different flavors so you should be able to find one you like. Good luck! -Jen

      • This could be a good alternative cause I do like yogurt. I’ll look for this brand…I always think of it as a snack so need to change my mindset to think of it as a meal. so the fats: what porportions do you use of peanut butter (I’ll probably use almond butter) to yogurt? about how many ounces of yogurt/PB do you eat to keep you satisfied till lunch? I’m going to need to think about this cause I only want about 4 oz of yogurt with a couple of almonds at a time and that is probably why I think of it as a snack.

        • Most flavors of Chobani have 2P 2C blocks (if you get the fat free variety). I think it’s a 6 oz to a container. Since there is no fat in it, you have to double the blocks of fat to balance out the meal – that would be 2 tsp of almond butter. As a note, I don’t mix my peanut butter in the yogurt, I just eat it on the side.

          • Really appreciate the math help! I am a picky eater and always tend to eat the same thing (thus the gag reflex after so many years) and haven’t had to think about the relationship between PCF in a long time so this is a big help. I did find this yogurt too and will have it tomorrow when I wake up! Many thanks, Nancy

    • Hi Nancy

      What about smoothies? You can use strawberries, blueberries, milk or yoghurt with almonds, macadamias, avocado etc and protein powder. Very filling. There might be some recipes on this site or there are some recipes in the Zone books.

      • I do like smoothies and also think of these as a weekend snack, mainly due to the clean up involved. I like the convenience of making the oats on a Sunday night and having breakfast ready to zap along with a few slices of Turkey bacon and a few almonds. I need to get out of the house pretty quickly in the morning. But let me see if maybe this is something I could prepare a couple of serving in advance and try the same thing for a quick morning exit. Many thanks for the post!

        • Hi Nancy

          Smoothies for me are breakfast most mornings. I too have to race out the door for work. The night before I put on the bench – my blender jug, shaker jug, container with measured protein powder, another container with nuts, defrosted strawberries and milk in the fridge. In the morning I measure 1 cup of milk with the shaker jug – nuts go in first and then add the other things – blend and all done! I sometimes process the smoothies the night before. Blueberries dont seem to work so well the night before. Other mornings for breakfast I have Dr Sears cereal or Zone granola. Just measure out 1 cup of milk into small bottle and take the bowl and spoon to work!

          • WoW! You rock! I think we could be roommates! I will definitely try this. I have a couple of more servings of oats made up that might not get eaten. I also am thinking about investing in one of those one drink blenders where the container/blender vessel is actually the cup. That might at least mentally make me think there is less clean up. Many thanks, Nancy

    • A good choice might be soy imitation meat products such as soy sausage coupled with the appropriate amount of low glycemic fruit such as berries. Likewise low fat natural yogurt is an ideal Zone breakfast. Mixing it with the Zone shakes gives an excellent pudding type of dessert that is great for breakfast.

  13. Dear Dr Barry,

    I first found out about the Zone diet through Crossfit- i trialed it owt for about a month in combination with daily aerobic and anearobic exercise and the results are amazing. Some new things ive noticed:

    1. increase in energy during the day and my mental alertness is sharp at work
    2. i feel fuller for longer and body responds now to eating every 2-3 hours.
    3. no more eczema- i have stopped sratching my body
    4. increase in physical performance esp in weight training.

    Coul you suggest a zone diet if i was lifting weights everyday e.g doing clean and jerks with heavy weights everyday?

    Many thanks

    • The Olympic athletes I have personally worked with have successfully used the Zone diet to win 24 Gold Medals in the past five Olympics. You may want to get a copy of my book, Mastering the Zone in which I detail those diets. I would also consider taking a day off every other day to give the body a chance to repair and regenerate new muscle tissue. The hardest thing for a athlete is do is get adequate rest.

  14. Many years ago, I followed the zone, ate very well balanced meals, lost weight, kept it off and had immense energy. You know the story- hypothyroid, eat the wrong foods equals weight gain. I am on HCG for 1 month and go off by the 2nd month and lost 22 pounds actually sculpting my body. My figure at 61 looks better than when I was 40. This was all done under a physician’s care and the HCG is Releana, a prescription HCG not something off the Internet, my doc will not have me on a maintenance of the Zone. He indicates that it is the only sensible way to eat.

    • Your physician is correct in recommending the Zone diet as a long-term sensible way to eat.

      HCG is a hormone that is produced by women during pregnancy that helps mobilize fat stores early in pregnancy. It can also help stimulate testosterone production. Although there are no compelling studies on its efficacy in weight loss, nonetheless it can provide an external stimulus to follow a very low calorie diet (about 500 calories per day). However a very low calorie diet is sure-fire prescription for eventual weight regain. Eventually, you have to have enough calorie intake to prevent loss of muscle and organ mass. The Zone diet will provide the necessary calories and more importantly maintain the hormonal balance necessary to prevent weight regain.

  15. Modern life [sic. electrification (with light) in your neighborhoods and personal spaces] is dangerous to our health. Now if we could just walk and climb 13 mi./qd, we would be in tune with out bioclock and genetic metablolic hardwires.

    “but you sure can sleep better and get thinner in the process if you keep the lights off. ”

    Thanks Dr. Sears, I can try to get my spouse to go along with the lights off.!!

  16. Dr. Sears repeatedly mentions cellular inflamation as a cause of many problems so I’d Like to know how Dr. Sears comes to the conclusion concerning cellular inflamation and how he test for this, especially cellular inflamation in the brain. Dr. Sears recommends fish oil to reduce the cellular inflamation in the brain but how can someone determine when the cellular inflamation has been reduced to the ideal level?

    • If you Google “Dr Sears and cellular inflammation” there are heaps of things to read. Have you seen his Toxic Fat book?

    • The brain can’t synthesize long-chain fatty acids such as AA, EPA, or DHA. They enter into the brain by crossing the blood-brain barrier from the blood. Thus the ratio of these fatty acids in the blood is a very good approximation of their levels in the brain. However, of the three fatty acids, only EPA is rapidly oxidized in the brain therefore its levels in the brain to reduce cellular inflammation can only be maintained by adequate levels of EPA in the blood. In my published work on the treatment of brain trauma (J Neurosurgery 114: 77-84 (2011)), we demonstrated that the reduction of the AA/EPA level in the blood resulted in a 98% reduced of axon damage due to a concussion injury. In our clinical studies, we always try to keep the AA/EPA ratio in the blood to a range of 1.5 to 3 as found in the Japanese population.

      The AA/EPA analysis is not a standard blood test, but is done in our laboratory for both our research studies and for determination of the optimal amount of fish oil a person requires to reduce cellular inflammation.

  17. Dr.Sears said last summer 2010 that his lab will be open to the public to test AA/EPA ratios. It is now almost April 2011 and he is promoting a zone cruise to Alaska. When will the AA/EPA test be available?
    I am curious about this cellular inflammation being the cause of most illnesses and the AA/EPA ratio needing to be in balance. Last year a biopsy revealed I had aggressive high risk prostate cancer and I had an AA/EPA test done in Canada for $150.00 and it revealed my EPA was too high in relation to my AA so a Zone specialist recommended I eat a little AA, like egg yokes, to increase my AA to get my ration in balance. Although my cancer is gone now, I have no idea what my AA/EPA ratio is today.
    Does anybody know what their AA/EPA ratio is or how much silent inflammation they have?

    • Unfortunately, the test is too expensive. That is one huge factor in my decision to NOT do the test. However, I am also waiting “patiently” to see a new test available via Dr. Sears.

  18. As related to cancer, what is the benefit of the test? When I had the test done, my AA/EPA was ideal and yet a biopsy revealed cancer. My thinking is that, even though you eat properly in the Zone and exercise (I walked an average of 5 miles most days for years) my PSA was elevated but steady for years (7 – 10 ng/ml) and cancer developed, regardless of an ideal AA/EPA.
    Also, April 29, 2010 a blood screening showed my Triglycerides 100 mg/dl, HDL 54.8, PSA 7.79.
    January 10, 2011 showed Triglycerides 79, HDL 83.7, PSA 0.09 after radiation therapy along with taking Dr. Sears Omega Rx 8 capsules a day.
    But I am still puzzled about taking a test that will show a person is doing fine when, actually, the person is not fine.

  19. I’ve been on your Omega 3 for over 10 years, the results on my blood work has been fabulous. Now reaching 70 has been a blessing thanks to you.

  20. On April 2 Dr. Sears said,
    “Half the people who have a heart attack have normal cholesterol levels”.

    On TV, the Lipitor commercial says 20% 0f people who have heart attacks have higher than normal cholesterol levels (or 80% of people who have normal cholesterol levels don’t have heart attacks).
    Somebody is not telling the truth. What is the truth?

  21. Have you ever thought about publishing an ebook or guest authoring on other sites? I have a blog based on the same ideas you discuss and would love to have you share some stories/information. I know my audience would appreciate your work. If you’re even remotely interested, feel free to send me an email.

  22. Wonderful site you have here but I was curious if you knew of any forums that cover the same topics discussed in this article? I’d really like to be a part of group where I can get responses from other knowledgeable people that share the same interest. If you have any recommendations, please let me know. Many thanks!

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