Many people are weight stable using the KetoFLEX 12/3 approach, but some find they begin to lose excessive amounts of weight when combining a long daily fast with exercise and our nutritional recommendations. This typically occurs when people give up unhealthy foods — sugar, simple carbohydrates, grains, and conventional dairy — but fail to add enough healthy fat into their diet to make up for the caloric shortfall.

Underweight Chart

Your HEIGHT isYour Weight is Under
4’11” —  5’2”100 pounds
5’3”   —  5’4”105 pounds
5’5”   —  5’7”115 pounds
5’8”   —  5’10”125 pounds
5’11” —  6’135 pounds
6’1”   —   6’4”150 pounds

Be aware that being underweight puts you at increased risk of sarcopenia (the loss of lean muscle mass) and osteopenia (the loss of bone), both of which accompany aging and are correlated with an INCREASED risk of cognitive decline. It’s important to adjust your strategies if your weight drops too low.

Helpful Tips

Consider shortening your fast. Try to stop eating several hours before bed to promote autophagy, “cellular housekeeping,” but feel free to eat three meals a day using the KetoFLEX 12/3 nutrition plan.

Use more healthy fat!!! A fear of healthy fat is far and away the most common reason for excessive weight loss. Increase heart-healthy mono and polyunsaturated Mediterranean fats. When enjoyed in the context of ample non-starchy vegetables (and no sugar or simple carbohydrates) they will promote vascular health.

Add an extra tablespoon or two of high polyphenol extra virgin olive oil (EVOO) to your salads and veggies. In addition to being high in calories, EVOO has been shown to improve brain structure, function, and cognition.

Enjoy an extra handful (or two) of nuts. Nuts are extraordinarily healthful and delicious. People who eat them live longer. Freely enjoy. Macadamias and pecans are especially helpful for weight gain.

Don’t forget avocado slices. These yummy, creamy fruits, rich in monounsaturated fats, are both high in fat and fiber.

Add coconut oil or MCT to your coffee. This is a simple way to increase calories and induce ketosis. The ketones from coconut and MCT oil may be especially helpful for those trying to gain weight, as lower dietary fats may prohibit the creation of ketones. (Be aware that these are saturated fats and may not be appropriate for those with cholesterol concerns. Mono and polyunsaturated fats [EVOO, avocados, nuts, and seeds] are more appropriate for this subset.)

Ensure that you’re getting enough protein in your diet. Your body cannot synthesize nor store the protein it needs for essential body functions. You must include it in your diet, or your body will cannibalize your muscles. Those who are underweight need extra protein. Several other groups may also need more protein, including those over age 65, those with chronic GI issues, and those recovering from toxic exposures. It’s equally important to ensure adequate stomach acid for the proper digestion of protein. You can use unfiltered apple cider vinegar in a small glass of water before meals or betaine HCL supplements with pepsin to increase acid.


Be strong. Be sure to concentrate on building strong muscles and bones. Devote a part of your exercise program (3 to 4x per week) to strength training and weight-bearing exercise.

Don’t forget resistant starches. Add a small amount of cooked and cooled legumes, root vegetables, or tubers at each meal. By using EVOO as a delicious topping, you’ll both blunt any glycemic response and add extra calories. Those who are struggling with insulin resistance may need to initially avoid resistant starches as they work on healing.

Get involved in meal planning and preparation. Scour recipes to find innovative ways to make your favorite foods to stimulate your appetite. If you’re cooking for someone affected with Alzheimer’s, involve them in meal planning and preparation. Seeing, touching, and smelling the food promotes the secretion of our digestive enzymes and prepares our bodies to eat.

Relax while eating. Turn off your TV and your phone. Put away your work. Make mealtime a nurturing and relaxing ritual. Eat mindfully, chew well, and slowly enjoy your food. Linger over a second helping.

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