David S. Ludwig, MD, PhD

The diet wars have been raging for years. Each side has ardent proponents–those who insist that a low-fat diet is the best way to control weight and those who are convinced that a low-carb diet is better have had a hard time finding common ground. Even those who endorse a more moderate approach can be emphatic about pushing their perspective, particularly those who insist that the only route is cutting calories and increasing activity.

Why Cutting Carbs May Be More Important Than Cutting Calories:

In November, 2018, The BMJ published a study showing that a low-carb diet was effective for maintaining weight loss. But that’s not all: the research showed that people eating fewer carbs had higher energy expenditure. This lent support to the low-carb crowd.

The Carbohydrate-Insulin Model:

Dr. David Ludwig, a principal investigator of the study, has written previously about “The Carbohydrate-Insulin Model of Obesity–Beyond ‘Calories In, Calories Out.’” His essay was published in JAMA Internal Medicine. He explains why refocusing on reducing carbohydrate intake rather than simply calories may be more effective for long-term weight control.

Dietary Fat–Friend or Foe?

In November, the journal Science published a commentary by Dr. Ludwig and three other nutrition scientists with widely different perspectives. In it, they reviewed the evidence on low-fat and low-carb diets and outlined where they found consensus and where there is still significant controversy.

Are all calories equal? The proponents of simply cutting calories count on it. But while this may be a basic law of physics, humans are not machines. The new research suggests that the relationship between calories, metabolism and weight may be more complicated.

This Week’s Guest:

David S. Ludwig, MD, PhD, is co-director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, a professor of pediatrics at Harvard Medical School and a professor of nutrition at Harvard’s T.H. Chan School of Public Health.

Dr. Ludwig has written three books for the public, including Ending the Food Fight, Always Hungry? and the cookbook Always Delicious. You may also enjoy reading his recent piece in the LA Times.

Listen to the Podcast:

The podcast of this program will be available the Monday after the broadcast date. The show can be streamed online from this site and podcasts can be downloaded for free. CDs may be purchased at any time after broadcast for $9.99.

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Air Date:January 19, 2019

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  1. Lance

    Another theory I’ve read about is resistant starches (another term for carbs). It is based on the idea of eating carbs that are slow to digest, thus not causing a blood glucose jump and contributing to colon health.

  2. Lance

    If the participants in a diet study were eating carbs that were mostly highly refined (white pasta, white bread), and then took on a low-carb diet, that is one thing. If the study included a group whose carb diet was based on whole grains, and then they cut down on those carbs, the results might show even more valuable info.

  3. Trish

    All my adult life I have struggled with my weight. I hear plenty of recommendations for balance of carbs, protein, & fats in percentages of total calories to eat each day. One would think this sounds easy. But the reality is that in this country we are so blessed with abundance of available food that most of us often have no idea that the amount of food we eat regularly is way more than needed or healthy. So, how does that 20%/50%/30% balance break down into just how MUCH food we should really be eating each day??

    I can’t maintain my weight on more than 1200 calories per day. That is reality. Here are my calculations for a basic 1200 calories/day food plan:

    For example at 20% carbs as recommended above, 50% protein, and 30% fat – one could eat 240 calories of carbs, 600 calories of protein, and 360 calories of fat each day.

    Use an average of 35 calories per 1/2 cup or 3 ounces of carbs = common vegetables like peppers, onions, carrots, broccoli, mushrooms, etc.; use an average of 100 calories per ounce of protein = meat, chicken, pork, fish, etc; and about 100 calories per Tablespoon of fat = oils, dressings, butter, sauces, etc.

    A common chicken stir fry with rice – each item weighed or measured – for me means: 3 ounces chicken (<300 c); 3 oz green pepper, 3 oz onion, 3 oz mushrooms (0); sometimes 1/4 c walnuts or almonds (> 150 c). Total calories = 315 calories give or take.

    This is carefully planned and weighed/measured and is almost 1200 calories in these two meals – and probably not even getting 600 c of protein. Difficult, you bet. Does it work? I am still 20-25 pounds overweight at 74 and cannot lose weight without eating less.

    That is reality!!! Of course you might tweak these estimates to bring this down, but no matter how much tweaking one does, this is not much food. We are blessed and cursed by abundance…

  4. Rita Loucks

    There are bad carbs and good carbs, bad fats and good fats. I’ve been following The Mediterranean Diet for years. Among bad carbs are anything with sugar added. Good carbs: fresh fruits and vegetables. Good fats include avocado, extra virgin olive oil, unprocessed nuts, wild caught Alaskan salmon (baked). Anything fried is bad. I’m in my mid-80s…and so far I am taking no prescription meds.

    • Larry

      FYI: The “Mediterranean Diet” was “designed” by someone who studied Med populations after WWII! … and he did not follow it!
      This was a time when most people around the Med had limited meat supply due to the war…
      this is why they were not eating much meat. not out of tradition.
      Med people’s traditional diets varied highly according to location.
      However they all aquired most, up to 70%, of their calories from highly nutritious, clean, healthy SATURATED ANIMAL fats from fish, pork, lamb/sheep, goats and some beef and yes olive oil. But major calories are from sat fats and everything else is flavorings and whole food based “fillers”…

      Actual research on traditional diets of non-industrialized peoples with minimal to no contact with industrial cultures, around the world, showed that they ALL ate a variety of animal fats, organ meats, meat (organs and fat are more nutritious), and fermented veggies.

      All traditional cultures fermented veggies, dried meats (includes fermentation during drying), ate the organs and blood of the animals they harvested made bone broth, rendered fats and made Pemmican like foods, etc…
      Any cultures that had grains and/or legumes fermented them all before cooking. Eating raw or unfermented veggies is rare.
      i.e. traditional Italian pasta is made from soaked (sprouted & fermented) grains.
      “Cellophane” (clear) noodles of asian cultures are made from fermented mungs (and other) beans.
      Everything traditional cultures did with food Maximized the nutrition of the foods.
      Today capitalist foods are made to maximized profits not nutrition.
      Junk food, sugary laced foods, Lack of optimal nutrition and env toxins, also due to capitalist greed for profits, are the main causes of all modern diseases of industrialized cultures.

      Traditional cultures, still eating their optimal diets, have all their teeth, no caries, rarely get sick, are tall, muscular, full boned beautiful humans who create health babies and keep their children healthy with highly nutritious hand and bacterially processed foods.

      Also fresh veggies are overrated!
      Fermented veggies if all kinds are much more nutritious.
      Fermentation destroys toxins and anti-nutrients like phytic acid and actually grows more vitamins and preserves the food longer and better than the frig (also highly overrated).

      All traditional Med sauces, like in all traditional cultures, are based on animal fats, broths, such that all Med carbs, like homemade pasta from fermented wheat berries, and garden veggies, many fermented, are slathered in butter and or bone broth based sauces.


      Here is the truth about fats…
      – Saturated animal fats are highly nutritious, have essential vitamins not available from any plant source including coconut oil.
      – Organ meats, skin, heads, brains, eyes, are much more nutritious than muscle meats. All ancient cultures ate these.
      – Sat fat, short chain fatty acids, helps maintain normal body weight and lose weight, and has full doses of vit A, D, K, K2, B12…
      – the body does not store sat fat as body fat it breaks it all down and stores it as glycogen and other molecules.
      – Veg oil, long chain fatty acids get stored as body fat thus tending to increase body weight
      – Vegetable oils are all extracts that we did not evolve eating.
      The oldest oil extract is olive oil. EVOO is great but again it is an extract and we have only been using it for a short time compared to evolutionary time.
      – Cholesterol does not cause heart disease.
      – Damage to arteries is one major cause.
      – Damage can be caused by ingested env toxins like air & water pollution, pesticides and herbicides (fat soluble), free radicals from burnt and rancid veg oils, burnt animal fats, sugar – from direct ingestion and high glycemic processed carbs.
      – After the damage, like scratches in an artery wall, the immune system sends out the handyperson cells who patch the damage with cholesterol – like duct tape, it can build up.
      Cholesterol is a repair tool not the cause of HD.

      Food that is produced naturally is good for you and the Earth which supports us unconditionally.
      Factory farmed foods are distructive of health in all it realms.
      Plus it contributes to malnutrition.
      Ancient traditional diets tend to be up to 10 x more nutritious than the modern “Standard American Diet.” how SAD for us!

      What to do?…
      – Eliminate added sugar
      – Eat only organic or clean sourced foods.
      – avoid all factory farmed meats, oils, dairy
      – Reduce carbs to a minimum.
      – Eat whole fat foods, no non-fat anything.
      – Learn to enjoy organ meats (sausage is a good way)
      – eat lots of fermented veggies like sauerkraut
      1 mouthful of sauerkraut has more probiotics than an entire bottle of most any probiotic supplement and the sk lacobaccilis is alive and growing unlike the dry supplement…

      Yours for New & Healthier Times, Larry

      – KPFA 94.1 FM: Pacifica Radio show “Your Own Health & Fitness” on air over 20 yrs! Layna Berman ND
      Community radio is uncensored by capitalist money, no commercials: sponsored only by individual listeners.
      You will only hear the vetted truth on community radio & tv.
      – The Cholesterol Myths – Uffe Ravsnov MD
      – Nourishing Traditions – Sally Fallon and her 3-4 other books
      – The Permaculture Book of Human Nutrition and Ferment – Bill Mollison
      – Nutrition and Physical Degeneration – Weston A Price DDS

  5. Mark
    Beckley, WV

    Impressive research and study design. Good show.

  6. Richard
    San Diego

    Carbs are very potent energy foods I’ve been told. A little goes a long way to supply energy. I cut back, survived easily and lost 55 lbs. in about 2 and a half months without any side effects or gnawing hunger.
    By low carb I mean one half banana a day in my ice-protein smoothie; a small veg salad with my dinner; maybe another veg or even a small microwaved potato with dinner, and no other carbs at all. Who knows if following this very low carb plan for a longer time is unhealthy.

  7. Tony
    Prachuap Khiri Khan

    The vast majority of people who diet and lose weight put the weight on again, and many increase it. There is only one way to lose weight, and that is to eat less. Intermittent fasting is simply eating less. Since carbohydrates have more calories than protein, if you cut down on carbohydrates you’re eating fewer calories. The whole diet scene seems like one massive effort by some people to make money and sell dieting products. At nearly 90 I tried every diet but failed to maintain a healthy weight until now. I eat less, and I have lost 25lbs.

  8. Kim

    I would love to see a study that pits healthy carbs against a low carb diet. I’m talking whole raw fruit, whole unprocessed grains, and legumes. I eat Mediterranean ethnically and often vegan or vegetarian as well as with animal proteins. I rarely eat any breads or pastas, but when I do, they are 100% whole grain. I might add less than a teaspoon of sugar to begin carmelization, but that’s very rare. There are just too many delicious recipes to repeat one very frequently.

  9. Cindy

    Dieting, in all its media glory, does not work–I agree. Listening to this show it all seems “common sense” and right in your face–literally and figuratively. Eliminating processed sugar, and once weaned, does–at least for me–let me pass these up without any and all “guilt” quite quickly. Thumbing my nose at a 6-layer dense chocolate cake gives me win-win energy! But too, sneaking in a slab of dark chocolate soothes when needed. A rather ying-yang, yo-yo self-prescribed prize when I need it. I think “starving” yourself from what you knew to eat all along makes no real sense. Easing into a new eating initiative makes it sound do-able and organic–no pun intended. I also think once you get weaned from “bad eating” the snowball effect occurs and you naturally want to keep the “good eat” chugging.

  10. Harry
    Williamsburg, VA

    I listened to today’s program with Dr. David Ludwig hoping that the conversation would include fasting. When to eat and when to sop eating. I have tried the high fat/low carb [HFLC] diet for years and have only seen my weight gain flatten, but not decrease. That is, until I heeded the advice of Dr. Jason Fung on one of your previous programs around Thanksgiving last year. Since that time, I have lost 20 pounds practicing various forms of intermittent fasting [IF] combined with the HFLC diet. Benefits have ranged from physical to psychological; from body weight and shape to sense of positivism and well-being. Please complete the picture for your listeners, of which I am a loyal fan for the past ten years. Consider a program which includes Dr. Ludwig with Dr. Fung. They compliment each other and they will best serve the public on this matter, which ranges far beyond obesity and into diabetes and its life threatening consequences. And thank you for your contributions to the nation’s health

  11. Cole

    I am familiar with eating without “dieting,” especially if it’s a balanced food intake of the correct things. Sometimes going on a hunger-strike type of diet backfires because when you starve yourself your body tends to hold onto fat rather than lose it. I’ve been on a long-term diet of eating very little, after thinking you don’t see many fat anorexic do you. So since starting in that way to be honest sometimes I don’t always succeed in fasting but have succeeded more than I haven’t. I’ve lost mega pounds which proves it can actually work.

  12. Bob
    South Carolina

    I’ve always had much more success cutting carbs than calories in losing weight. However, I always gain it back because I enjoy eating all foods, as to me this is one of the great joys of life.:):)

  13. Mark

    I have done low-carb eating three times. It worked great the first time. Not at all the second time. I lost weight the third time but the constipation was terrible, and I was pretty sure it was harming my health. I have a buddy who’s really big on low carb, keto, etc.. He’s skinny and runs marathons. He has no history of heart disease in his family. He just had a widow -maker heart attack. Point I’m driving at is, eating a high animal fat diet of any description just seems like a terrible idea in the long run. I will never do that again.

  14. Paul

    Yes. Carbs (sugars) take away from my focus on getting the 65 grams of protein to build and maintain my muscles, as explained in the April 2011 issue of a nutrition action newsletter.

  15. Joan
    Buffalo NY

    I feel much better when I eat fewer carbohydrates. I think you just need to use common sense about balancing fats. Limit them to the good fats and yes, on occasion take a little splurge. If you feel deprived, that is when a major foodfest will creep in. Balance your diet with a focus on fewer carbs.

  16. Fred
    Mims, Florida

    It is nice to see that the mainstream medical establishment is finally learning what Dr. Barry Sears, PhD Biochemistry, has been writing about for over twenty years in his many books about his Zone diet, which balances protein, fat and carbs to prevent excess insulin from defeating our attempts at dietary weight loss. My favorite book of his is called “A week in the Zone” and covers everything you need to know to implement this fantastic way of eating and losing weight. My weight went from 320 pounds down to 180, with a loss of about 2 pounds per week, and with no excessive hunger due to eating less.

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