Stephanie Wagner is a bariatric dietitian who has her own website and blog to assist bariatric patients before and after surgery achieve their goals. She came to address all the popular fad diets that folks are hearing about on social media sites and if they are effective or safe for patients after bariatric surgery.  Her website is

The latest diet programs most frequently mentioned on social media are:

  • Keto and Paleo
  • Weight Watchers
  • Vegan (several varieties)
  • Whole 30
  • Intermittent Fasting and Carb Cycling

When looking at any diet, the first two questions to ask are:

  1. Does it totally contradict your bariatric diet recommendations?
  2. Is it sustainable – in other words is it something you can maintain long term?

To answer those questions, you need to first review the basics of the post-op bariatric diet:

  • Protein first – aiming for around 60 grams of protein a day
  • Non-starchy vegetables next
  • Limit fruits, and when eating fruits be sure to pair with protein
  • Limit heart healthy fats
  • Avoid high starch vegetables, sweets and saturated fat
  • Take small bites and eat slowly
  • Avoid drinking with meals; but aim for 64 – 96 ounces of sugar-free liquids a day

Let’s take a look at each of the fad diets individually:

  1. Ketogenic – the goal is to keep carbohydrates to a minimum and increase fat. It plans on having you get 60 – 75% of your calories from fat, from things like “fat bombs”  and “bullet-proof coffee”
    • It doesn’t completely contradict the bariatric diet, but it emphasizes fat instead of protein
    • Too much fat is very hard on the post-op GI system – it will have difficulty breaking down that much fat and can cause dumping syndrome
    • High fat is high calories, because 1 gm of fat = 9 calories, where 1 gm of protein or carbohydrate = 4 calories
    • Reaching your protein goals are very difficult on this diet, and at the end of the day, you need to take in less calories than you burn off
    • A way to modify this diet for post bariatric surgery is to keep your protein to fat ratio at 1 to 1 – 1 grams of protein to 1 gm of fat; and keep your carbs to under 30 grams a day
  1. Paleo (paleolithic, or caveman) – the goal is to eat only unprocessed foods that our ancestors would have had access to, such as leafy greens, pesticide-free veggies, nuts, fruits on occasion, grass-fed meat, pasture raised poultry, and wild-caught fish.
    • It is naturally low in carbohydrates because it eliminated processed foods, and still focuses on meats and protein, so it doesn’t contradict the bariatric diet
    • You need to watch the “paleo friendly” foods and desserts as they may have more carbohydrates than are recommended for after surgery
    • This diet is frequently paired with a high intensity workout program such as Crossfit
    • It calls for root vegetables, which tend to be very high in carbs, such as carrots, potatoes, sweet potatoes – those all convert to sugar very quickly, and then your body will burn those instead of burning fat
  1. Weight Watchers – this program has been around for a long time and frequently changes. It does require you to join in to get the full benefit.  The latest version is “Beyond the Scale” which started in 2017.
    • Uses a point system, and has over 200+ foods that have zero points so you don’t have to track
    • You track your points and can rollover points to another day to provide flexibility
    • The biggest benefit is the weekly weigh ins that help to hold you accountable every week
    • While it doesn’t contradict the bariatric diet, you need to be very mindful of zero-points foods, as those are more designed for patients who have not had surgery.  They also don’t prevent snacking, which does contradict the bariatric diet.
    • It is sustainable as long as you continue to get 60 – 70 points from protein, and get 3 meals a day
  1. Vegan – the goal is to eliminate all meat and products made from animal sources. There a lot of variations, but a strictly vegan diet severely limits protein sources to fruits and vegetables, beans, edamame (soy), tofu and textured vegetable protein.
    • While it doesn’t contradict the bariatric diet, it is difficult to sustain as it is very challenging for someone to stay full on a completely vegan diet, as non-meat protein sources leave the stomach much faster
    • This diet is usually one chosen by someone for ethical reasons, and is more about personal convictions than weight loss
  1. Whole 30 – This is a copyrighted program that focuses on eating only “real foods” – nothing processed.
    • Is designed to be used to eliminate certain foods for 30 days: no sugar (real or articial), no alcohol, no grains, no legumes (beans), no dairy, no baked foods, no junk foods or treats.
    • Is doesn’t contradict the bariatric diet, but is actually more restrictive
    • You need to have a plan to go to after those 30 days
  1. Intermittent Fasting – this is more of an eating PATTERN where you cycle between eating and fasting, but doesn’t tell you what to eat. There are several eating patterns you can use, but most commonly recommend you eat during an eight hour period each day, and then fast the other 16 hours a day, taking in only sugar-free liquids.  Some have you eat for 5 days, and then fast for 2 days. 
    • This does contradict the bariatric diet, which wants you eating 3 meals a day. While you can eat your 3 meals within the 8 hour period, our dietitians never recommend fasting beyond 48 hours. 
    • There isn’t a lot of scientific evidence to support this diet yet, and this can be hard on your metabolism, which wants to slow down when you are fasting.
    • If you have diabetes, you must be extremely mindful of your blood sugars; and this can increase your cravings for carbohydrates, so that when you stop fasting you eat a lot of carbs.
  1. Someone asked about Carb Cycling – this is designed more for people who work-out a lot and is more of a maintenance diet. You eat more carbs on one day, less on another, and it requires 5 meals a day, so it contradicts the bariatric diet. 

If you want to try any of the above programs, meet with one of the dietitians to help you modify them to be bariatric appropriate.  Good luck!