I just had to say, first and foremost, that thumbnail is hilarious! In my experience, it's a good sign that transition has been made too quickly. I'm convinced that most of the time it's microbiome dysfunction. Remove carbohydrate too quickly and one is prone to mass die-off of certain microbes (like ruminococcus and bacteroides species) which can result in overpopulation of other microbes (like faecalibacterium, and akkermansia) and I have had a great deal of luck in adding back a bit of whole food carbohydrate (I favor starchy veg) for several weeks, until the movements normalize, then transitioning again more slowly. There's no real way to predict how long the gut microbiome will take to rebalance when plant sourced foods are withdrawn. I always recommend SLOW transition; 4 weeks at minimum, 8 is better. Anyone who has chronic digestion issues should take a period of months, imho.

@James Dawkins Indeed! Those stories of overnight transitions resulting in 30 day cures of everything from dandruff to cancer are so entertaining they get all the attention, nobody realizes its only about 10% of people who slam over like that can sustain it. Nor should they! Severe gut dysbiosis can become life threatening, although, admittedly, that's rare. But being bloody miserable for 6 weeks to 6 months is common with rapid transition.

Overconsumption long term results in increased body adiposity, no matter what kind of food it is. Let's get that correct right off the bat. A better question would be "Are high fat diets associated with overconsumption?" The evidence we currently have suggests that a high fat diet is associated with DECREASED consumption in an ad libitum carnivore or carbohydrate restricted eating pattern. This nonsense is left over from the disastrous 7 Countries Study. I try to interest clients in learning about human metabolism. Once they begin to understand what's REALLY happening with their bodies, they can begin to see through the BS, and they get very motivated.

I like to say "OK, what you were eating didn't work, we'll find something that will." If they really want to continue, as Isabel says, they'll be willing to troubleshoot with you. If they don't seem interested in figuring it out, they've probably just decided they don't want to do it, for whatever reason. At that point, we need to have a talk about why it doesn't feel doable.

If a client is on drugs for T2D I don't recommend fasting, unless the client feels comfortable not taking their insulin moderating medication for the duration of the fast, & even then, I wouldn't be on board with more than 24 hours. On top of that, we would almost invariably have to talk about how they feel about going against their doctor's recommendations. Other than that, the only other reasons I would not recommend extended fasting is; necessary meds that must be taken with food, body adiposity too low, uncontrolled thyroid dysfunction, or body dysmorphia/anorexia. Most people can work up to a longer fast if they want to try it, & if they don't, I just recommend narrowing their feeding window to 12 hours or less to start with.

HOLY GUACAMOLE! Where do I begin! The most important change (and it cannot be overstressed) is MENTAL HEALTH! Every single person I have helped has told me that something in their brain has gotten better. Mood, concentration, sleep, stress, irritability, anxiety, brain fog, coping with addictive behaviors, or even just the capacity to be less pessimistic. Perhaps not all of these at the same time, but something will improve and it usually happens pretty quickly. An improved mood is like magic! I like to point out that metabolizing fat usually produces ketones, and explain that ketones are better brain fuel than glucose. I like to say running your brain on glucose is kind of like trying to run your modern car on diesel fuel. It will work, but not very well, and only for a while before the system crashes. But mental health improvement is only the beginning! How about less acne/improved skin, no body odor, no bad breath or dental caries, REVERSAL of periodontal disease (THAT'S not supposed to happen 😆), remission of autoimmune conditions, improved digestion, and improved fertility and sexual function. I've even known people who insisted their prescription for eyeglasses changed for the better!