To Keto or Fast? What Diet Works?


Diet fads come and go but what actually works? Some diets have scientific basis behind them but many do not. Understanding diet and nutritional choices is a full-time job and I am not a nutritionist, so finding what works and why it works is always part of the challenge for me as a fitness writer.

My go-to answers are in the form of scientific studies as well as opinions of nutritionist and registered dietitians (see list below). But, here is a question that is tough to answer as it pushes outside my comfort zone, but I do have personal experience and links to studies for you to consume:


Now in my late 40’s, I am looking at losing weight. I need to - actually. I have come to the age where outworking my diet (like you say) is not in the cards, so my intake needs to change.  I have been reading about intermittent fasting and ketosis diet planning.  Do you have a recommendation on either or a different one perhaps?  Jason

My experience (one month of ketosis):

It took nearly a week to get into ketosis (checking with keto urinalysis strips). During that week, I lost 3 lbs. not because I was in ketosis, but because I took out 30-40% of my daily calories from carbohydrates (breads, grains, snacks, juice) though I did eat tangerines, broccoli and asparagus to the tune of about 50 grams of carbs in a day. Still the reduction in calories per day caused the weight loss – not ketosis.

Once in ketosis for about 3 weeks, weight loss continued to occur. However, one day on a fat and protein binge (steak and chicken), I took in about 5000 calories that day. I did not burn off that many calories that day, so the result was a calorie surplus and weight gain regardless of ketosis. It took another 36-48 hours before I was losing weight again – even though in ketosis. So, you cannot eat all the protein and fat you want as your body still has to metabolize what it consumes. Moderation and portion control still play important roles.

Energy to Workout

Early morning workouts on low carb diet required some back up carbs to “stay in the game” sipping about 15-20 grams of carbs in Gatorade helped with the light-headed effect. Or, you can drop the intensity and just do some lower impact cardio and avoid the carbs if you prefer. But after about 30 minutes of normal workout activity, dropping the workout to lower impact / lower heart rate (less than 120 bpm) was helpful to staying active (swimming, slow jog/walk, and biking).

Here is the thing about fasting diets / lower carb diets from my experience:

Portion Control: A diet that creates a caloric deficit will work for reducing body fat. You do not have to be in ketosis to lose fat. So, you can still eat carbs, proteins and fats, but if you control portion size and create the deficit by eating less and moving more, you will lose weight.

Fasting Options: Fasting is not the optimal method to weight loss, but it can work temporarily if you do not mind getting “hangry” and lack energy to train or think for that matter. The term “intermittent fasting” has become popular that allows for a particular time of day to eat, then the rest of the day / night you avoid food altogether. This one requires discipline – like most diets, but as creatures of habit it can work for some. At the end of the day, it truly comes down to you having eaten less than normal – creating that caloric deficit. In fact, fasting can be detrimental to muscle growth (catabolic) so consider carefully how you implement this one.

My recommendation is try and see if you like them.  I am a big fan of reducing if not completely (almost) eliminating sugar from a diet. I think too much sugar is a health risk too many people do not realize.  So, start with reducing sugar, drink more water, smaller portions, and exercise for 30 minutes a day.

References and Related Articles:

Collection of Studies on Keto / Lower Carb

Keto Diets, Fat Loss, Muscle Performance

Energy and Ketogenic Diets

1000 calories in or out

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