By Dr. Mercola
Calorie restriction has been scientifically proven to slow down aging, extend lifespan, and even reduce the risk of age-related chronic diseases such as cancer.
Newer research is now showing, however, that strategically restricting your calories may also be an effective form of cancer prevention and treatment. As a leading cause of death worldwide, the incidence of cancer is on the rise, despite the decades long 'war on cancer' that conventional medicine has waged against this disease.
As simple, natural methods continue to prove their merit, it's becoming clear that what are now viewed as alternative methods of cancer treatment may soon become regarded as the standard of care, and calorie restriction may be among the top go-to options.
Short-Term Calorie Restriction Improves Cancer Survival
A new animal study tested what would happen when mice with lymphoma were fed a regular diet or a calorie-restricted diet (75 percent of their normal intake) along with a targeted therapy to induce cancer cell death (known as ABT-737).1 The idea was that the lower caloric intake might limit the expression of certain proteins associated with cancer. As explained by the American Society of Hematology:2
"When humans and animals consume calories, the body metabolizes food to produce energy and assist in the building of proteins. When fewer calories are consumed, the amount of nutrients available to the body's cells is reduced, slowing the metabolic process and limiting the function of some proteins.
These characteristics of calorie restriction have led researchers to hypothesize that reducing caloric intake could potentially help inhibit the overexpression of the protein Mcl-1, an alteration associated with several cancers."
The study showed that calorie restriction did improve survival when done along with the treatment. Specifically, median survival was 30 days in the control group that received a regular diet and no treatment, compared with:
- 33 days in mice that received a regular diet and treatment with ABT-737
- 30 days in mice that received a reduced-calorie diet without treatment
- 41 days in mice that received a reduced-calorie diet and treatment with ABT-737
Furthermore, the number of circulating lymphoma cells was reduced in the calorie-restricted/ ABT-737 mice, which suggests that the cancer cells had been sensitized to the treatment.
Is Calorie Restriction the Most Important Aspect of Cancer Prevention and Treatment?
In order to maintain and sustain nutritional ketosis, you need to decrease both carbohydrates and protein. But how much protein is enough or too much? Dr. Seyfried is more cautious in his evaluation of reducing protein for cancer prevention, but one of my mentors, Dr. Ron Rosedale, advocates restricting protein to one gram per kilogram of lean body mass. Typically, for someone like myself, that amounts to about 50-70 grams of protein per day.
The reason he promotes this so much is because of the stimulatory effect protein (branch-chained amino acids specifically) has on mammalian target of rapamycin (mTOR)—a pathway that seems to be largely responsible for the pathology seen in cancer growth. Dr. Dominic D'Agostino, PhD, an assistant professor at the University of South Florida College of Medicine, also believes protein must be restricted for cancer prevention.
He explained in our interview (see the video above):
"The ketogenic diet is, I think, a very good strategy to make calorie restriction tolerable. Because when your brain in particular is craving glucose, and, say, for example, you go on a calorie-restricted diet, but it's a high-carbohydrate diet, you're still getting fluctuations in blood glucose. Your brain goes through these intermittent periods of glucose deprivation and you get very hungry. It's not a very comfortable feeling.
Nutritional ketosis, which occurs with carbohydrate restriction and is further enhanced with calorie restriction, forces the physiological shift from a glucose-based metabolism to a fatty acid and ketone metabolism. When your body is, shall we say, keto-adapted, your brain energy metabolism is more stable and your mood is more stable. It may take a few weeks to adapt physiologically to this. But nutritional ketosis can be maintained and sustained with carbohydrate restriction and is further enhanced with calorie restriction.
The total calories really need to be restricted, and also protein. Protein is gluconeogenic. There are gluconeogenic amino acids in protein. If protein is at, say, for example, two or three grams per kilogram per day that is probably going to feed in through the gluconeogenic pathway and contribute to glutaminolysis. It will be hard to deplete your glycogen stores, which is necessary to drive the ketogenesis in your liver."
Calorie Restriction Is Essential for Cancer Patients, But Is an Important Cancer-Preventive Strategy, Too
From my perspective, it's medically unethical to fail to integrate this safe and effective dietary strategy into a patient's cancer treatment plan (along with optimizing vitamin D). A ketogenic diet along with intermittent fasting can be easily integrated into whatever cancer treatment plan you decide to follow. Personally, I believe it's absolutely crucial, no matter what type of cancer you're trying to address.
To get more specifics about using a ketogenic diet and calorie restriction for the treatment of cancer, I highly recommend picking up Dr. Seyfried's book, Cancer as a Metabolic Disease. You can also review his papers,3, 4 which outline the guidelines and treatment strategies for cancer patients. If you're a cancer patient, I'd recommend printing them out for your oncologist.
That said, remember that a ketogenic diet, in which you replace carbs with low to moderate amounts of protein and high amounts of beneficial fat, like avocado, coconut oil, butter, olive oil and macadamia nuts is recommended for everyone, whether you have cancer or not. It's a diet that will help optimize your weight and health overall, as eating this way will help you convert from carb burning mode to fat burning.
Want to Try Calorie Restriction? Try Intermittent Fasting
While the research supporting calorie restriction is compelling, it's not a very popular dietary strategy for most people, for obvious reasons. Many are simply not willing to deprive themselves of calories to the extent needed to prompt the beneficial effects. An alternative that is much more acceptable is intermittent fasting, which can be as simple as restricting your daily eating to a narrower window of time of say 6-8 hours (this equates to 16-18 hours worth of fasting each and every day).
Recent research suggests that sudden and intermittent calorie restriction appears to provide many of the same health benefits as constant calorie restriction, including extending lifespan and protecting against disease.
Unless you have a very serious disease, I believe it is best for most people to implement intermittent fasting slowly over six to eight weeks. You begin by not eating for three hours before you go to bed, and then gradually extend the time you eat breakfast until you have skipped breakfast entirely and your first meal of the day is at lunch time. Of course, you are only consuming non-starchy vegetables for carbs, low to moderate protein and high-quality fats. One of the things I've noticed is that once you've made the transition from burning carbs to burning fat as your primary fuel, the desire for junk foods and sugar just disappears like magic.
It typically takes a few weeks for most to shift from burning carbs to fat-burning mode. Once you succeed and switch to fat-burning mode, you'll be easily able to fast for 18 hours and not feel hungry.