Fad Diets for Health and Fitness

Do Extreme Diets Work?

Healthy eating is complementary to physical activity in maintaining a lean weight, fitness, strength and all-round good health. In fact eating correctly can be crucial to sports performance and competition success in athletics, team sports and bodybuilding and powerlifting to name a few sports.

The question arises as to whether a very specialized diet limited in food choices has advantages over the generally accepted healthy eating pattern recommended by nutrition authorities and sports nutritionists.

In summary, healthy eating guidelines are:

• Eat plenty of fruit and vegetables, whole grains, beans, nuts and seeds; some lean meats, fish, eggs, and low-fat dairy products; and mono and polyunsaturated oils


• Limit intake of saturated fat, cholesterol, salt, alcohol and an excess of added sugars and sugary foods


• Drink plenty of water


• Maintain a normal weight


• Exercise regularly.

Even within these guidelines the percentages of macronutrients such as carbohydrates and fats and protein can vary.

While the most recent dietary guidelines list the acceptable macronutrient distribution ranges for carbohydrate, fat and protein as 45-65%, 20-35% and 10-35%, respectively, trained dietitians and nutritionists would only very rarely recommend protein percentages higher than 25 percent of total calories.

Fad Diets and Extreme Diets

As many readers will know, special diets on the fringe of these ranges of macronutrients or food selection boundaries are common and popular as evidenced by the number of successful diet books doing the rounds. In any case, I have identified five types of dietary regimens that I call ‘extreme’ diets; not because they are necessarily unhealthy but because they are restrictive and require careful planning and nutrition knowledge in order to meet all the required nutrient requirements for health and energy purposes. Here they are:

1. Very low-fat diets


2. Very low-carb diets


3. Vegan and macrobiotic diets


4. Paleo diets


5. Fad diets such as metabolic type, blood type, raw food

Let’s go through them one by one and deal with the ‘gotchas’ for each one – especially in relation to exercise and weight training where applicable.

Very Low-Fat Diets

Very low-fat diets are characterized by the Pritikin and Ornish diets which take the name of the creator. Both recommend that very low quantities of fat of any type is consumed, and this is usually in the range of 10-15 percent of total calories. The Ornish diet is a near-vegan diet with no meat and only low-fat dairy foods providing animal protein. No fish, nuts, avocados or olives are allowed. The Pritikin diet does allow some low-fat and lean fish, chicken and beef in small portions. Both emphasize mostly fruit, vegetables and whole grains and beans and little added sugar and refined grain foods.

Pritikin Longevity Center
Dean Ornish Lifestyle Program

What can go wrong with very low-fat diets?

Carbohydrates. A regular exercise program requires carbohydrates to fuel that exercise. It is the number one fuel for the more intense activities such as weight training especially if you combine it with circuit type training and strong cardio workouts. Very low-fat diets like Pritikin include a lot of high-fiber carbohydrates, usually 75 percent or more, so you won’t be deficient on a very low-fat diet.

While refined and high-GI carbohydrates such as added sugar and white bread are not encouraged on these diets, if your exercise program includes high volume -- either intensity or duration of exercise -- you may find that you have trouble eating enough to fuel your activity if you consume a very high-fiber diet. Food fiber is bulky and creates satiety -- the feeling of being full. Some refined carbohydrates before, during or after exercise may be helpful.

On the other hand, as a general health consideration, low-fat, high-carbohydrate diets can go terribly wrong if you make the mistake of following the low-fat part without the high-fiber part. Diets high in refined carbohydrates and sugars tend to raise triglycerides and lower HDL, the good cholesterol, in the blood which may elevate heart disease risk.

Protein. While exercise, even weight training, does not demand an extraordinary amount of extra protein, it does require some extra, and serious weight training activities require the most. The very low-fat diets tend to de-emphasize protein intake, so you would need to ensure diet plans provide a solid protein supply in the range 1.5-2 milligrams/kilogram bodyweight/day. (Half this per pound of bodyweight.) Higher protein diets may assist with weight loss as well. Raising the protein content of very low-fat diets to at least 20 percent of caloric intake would go some way toward addressing protein requirements.

Essential fats. A regular criticism of very low-fat diets is that they could be deficient in the omega-3 and omega-6 essential fatty acids considering that nuts, avocados and oil seeds are generally discouraged and in the case of the Ornish diet, fish as well. The answer to this is to include at least some omega-3 rich fish such as salmon or sardines regularly and to be less strict with wholesome foods such as nuts and avocados. With a low fat intake also comes the risk of insufficiency, if not deficiency, of the fat-soluble vitamins A, E, K, and D.

Vitamin deficiencies. The Ornish diet risks being deficient in vitamin B12, iron and zinc because it precludes meat (see vegan diets below). Women require about 15 milligrams of iron each day, men about 10 milligrams and some athletes and heavy exercisers may require more. While fortified foods like breakfast cereals and soy milk can supply iron and B12 in useful amounts, a B12 supplement may be required in meat-free diets unless fortified foods can be identified and consumed regularly.

Summing up very low-fat, if you exercise regularly and intensely you must make sure you get enough energy, protein, fatty acids, iron and zinc in these diets.

Very Low-Carb Diets and Exercise

What's Wrong with Very Low-Carb Diets?

For this evaluation I make the distinction between diets that restrict carbohydrate to around 45 percent, and diets such as Atkins and others that would have you eat less than 30 percent carbohydrates or indeed induce ketosis (very low-carb), a condition where fats are converted to chemicals called ketones to fuel the body when stores of glucose are exhausted.

What can go wrong with very low-carb diets?

Carbohydrates. While the body can adapt to some extent to low-carbohydrate, high-fat diets for exercise, weight lifters and others involved in high-intensity exercise need glucose to fuel the intense activities of weight lifting (along with the ATP and phosphocreatine systems). Fat-fueled exercise is possible -- walking and slow jogging are examples -- but as soon as you make demands for high intensity such as sprints, intervals, circuits or heavy lifting, then your performance and your training will suffer.

The reason for this is that high-intensity exercise needs fuel supplied to the muscles quickly. Fat cannot supply ‘quick fuel’ sufficiently fast, while carbohydrates can.

For some weight trainers, a low-carbohydrate diet can be problematic in relation to maintaining muscle mass. Protein is not a good substitute for carbohydrate for weight trainers for the following reasons. Although excess protein can be broken down to form glucose, this process is limited and and cannot substitute for carbohydrate’s supply of glucose. In addition, low levels of carbohydrate can stimulate production of the hormone cortisol which breaks down muscle protein to supply the body with glucose – the last thing a body builder or weight trainer wants.

Some experienced weight trainers use a cyclical ketogenic diet where they do very low-carb for a few days and then revert to a high-carb diet to get an insulin rush and, supposedly, build muscle. I'm not convinced of the value of this and I know of no scientific evidence that it works. Don't bother with it.

Protein. Low-carb diets usually supply plenty of protein so insufficiency is not going to be a problem for weight trainers and exercisers. Very low-carb diets can require that up to 35 percent protein is consumed. However, if you’re looking to lose weight with a very low-carb diet you need to be sure that your kidney function is normal. High-protein diets are not recommended for people with chronic kidney disease as this may exacerbate the disease. Very high-protein diets of mostly meat protein may also cause excessive calcium excretion as the body attempts to buffer acidity. Osteoporosis (bone loss) may occur as a result. This may be prevented by a sufficiently alkaline diet high in fruit and vegetables but therein lies the risk. In addition, too much red meat in the diet may increase risks for bowel cancer and possibly type 2 diabetes. High-protein diets may be healthier when red meat is restricted in favor of white meats, low-fat dairy and vegetable protein.

Vitamin deficiencies. On the Atkins diet and other very low-carb diets, excluding whole grains can make it difficult to get enough fiber, magnesium, thiamin (B1), and possibly folate. Without dairy foods, calcium, vitamin D and riboflavin can be in short supply. Restricting fruits and starchy vegetables limits vitamins A and C, potassium and folate. In addition, cholesterol and saturated fat intake exceeds that recommended by the American Heart Association.

Summing up, a very low-carb diet is not suitable for an active person. In fact, if you are very active and exercise four or five days a week at moderate to high intensity, even a somewhat low-carb diet is likely to be sub-optimal. For weight loss and general fitness, moderate low-fat diets higher in carbohydrate are likely to be more suitable.

Vegan Diets and Exercise

What's Wrong with Vegan and Macrobiotic Diets?

I have included these two dietary regimens together even though macrobiotic diets often allow animal foods, mainly fish. Many macrobiotic dieters are vegans too. Vegan diets allow no animal products at all, even eggs. Macrobiotic practitioners include a high proportion of whole grains, particularly brown rice, and have a particular requirement for preparing foods according to principles handed down over many years and originating in Japan.

What can go wrong with vegan diets?

Protein. Generally speaking most vegan and macrobiotic diets are relatively low in protein, perhaps in the range 10-12 percent of total energy. This is because meat, dairy and egg consumption restrictions limit the total protein consumed in favor of beans and nuts, perhaps fish, and grains and vegetables, which provide smaller quantities.

Weight training on a vegan diet is not impossible, but attention must be paid to sufficient protein and sufficient energy, particularly if bodybuilding is your goal. For sport in general, there are many fine examples of world class sportspeople who followed vegan diets. Dave Scott, the world’s best triathlete in his era and multiple Hawaii Ironman race winner was a very successful vegan athlete.

Dave Scott was a great believer in copious nut consumption for vegan athletes. Nuts supply some protein and also provide essential fats like omega-3 fats, particularly walnuts. In addition they supply energy which is often lacking in vegan athletes doing extreme training. Vegan bodybuilders and weight trainers should attempt to get their protein percentage up around the 20 percent mark or at the 1.5 to 2 grams/kilogram bodyweight per day intake.

Creatine. Creatine is a constituent of meat and creatine is also a useful bodybuilding supplement with applications in power sports for building body bulk and enabling high-intensity training. Vegan diets are very low in creatine. Vegan creatine supplements may be available from some sources. Ask suppliers about the origins of their creatine if this supplement interests you.

Carbohydrates. Vegan diets are usually high in carbohydrate, in the range 65-75 percent, and high in fiber. As noted above in the section on very low-fat diets, athletes who need to consume large quantities of food to fuel their exercise habits may not find high-fiber diets easy to manage. To consume 3000-4000 calories a day some simple sugars and refined carbohydrate foods may be required, especially in the post-exercise recovery meal. If you're attempting to lose weight, don't go overboard with the refined sugars and breads though.

Vitamins and minerals. Vegans are frequently deficient in calcium, iron, zinc, vitamin D and vitamin B12 measured against recommended dietary intakes (RDI). Calcium is available in green leafy vegetables and nuts and beans, and yet vitamin D can be an issue for bone health and vegans should deliberately seek sufficient sunshine exposure to enhance vitamin D absorption. Iron and zinc are not absorbed as efficiently from plant foods as from animal foods so vegan exercisers and weight trainers need to ensure sufficient intake.

Fortified foods such as breakfast cereals and soy milk and specially formulated vegan foods can ensure sufficient intake of these vitamins and minerals. A quality multivitamin supplement is a simple way of solving potential deficiencies for vegans. Vegans who follow a raw food diet are likely to be more susceptible to such vitamin and mineral deficiencies. (See more on raw food diets below.)

Essential fats. See the section on Very Low-Fat diets above. Similar cautions apply to vegan diets. The regular consumption of nuts may provide some assurance that possible deficiencies are averted.

Summing up, vegan diets can be constructed adequately for athletes as many have proven. However, attention to detail is required for total energy, essential fats, protein, iron, calcium, zinc and B12. Vegan diets may not be optimal for weight trainers wishing to bulk up.

Paleo Diets and Exercise

What's Wrong with Paleo Diets?

Often called cave-man diets or Neanderthal diets, Paleo diet principles implore us to return to hunter-gatherer practices of the Paleolithic period of human evolution more than 10,000 years ago. This requires that we refrain from eating grain foods, potatoes, beans, milk, and refined sugars -- foods only eaten within the last 10,000 years and which are deemed to be unsuitable for consumption because of an insufficient time for Homo sapiens to adapt to these foods. The Paleo diet is high in meats, vegetables and fruit.

What can go wrong with Paleo diets?

Protein. As with all high-protein diets, the caveats above in the discussion on very low-carb diets apply. However you won’t have a problem getting sufficient protein for exercise on this diet.

Carbohydrates. Although fruit consumption is encouraged, this is still a relatively carbohydrate-restricted diet.

Heavy exercisers may find it difficult to consume enough carbohydrate to fuel their activity without some sugar and grain foods. Heavy fruit and vegetable and fiber consumption also has potentially disastrous implications for social acceptability at the gym considering the flatulence that many people are prone to. This is not exactly the savannah or rain forest!

Essential fats. Paleo dieters make a special point about the omega-3 to omega-6 fat ratio, which they say is skewed too much in favor of omega-6 fats found in seed oils and nuts. Omega-3 fats from fish feature strongly in the Paleo diet.

Summing up, the Paleo diet could be a healthy diet with restrictions on red meat and saturated fat and cholesterol accompanied by sufficient fruit and vegetable consumption. For vigorous athletic activity, including weight training, Paleo diets may have to be modified to make allowances for additional and alternative carbohydrate consumption.

Fad Diets – Blood Type, Metabolic Type, Raw Food

Last in the list are diets which I suggest are gimmicks or at least scientifically unproven or even biologically illogical. I won’t spend much time on these other than to say that you don’t need them, and some may even be unhealthy, the raw food diet being an example.

You can tell a fad diet by the fact that you either need to choose components very carefully according to some characteristic of your body or metabolism, the scientific basis of which is either absent or wildly extrapolated from only mildly relevant research; or to comply with a perceived healthy eating era, region or esoteric premise or religious requirement.

Summing Up Extreme and Fad Diets

The basic principles of eating for health and physical activity are clear enough: don’t get waylaid by extreme diets. You don’t need them for healthy living and above all you don’t need them for weight training. See the Bodybuilder’s Weight Training Diet for more detail of a suitable diet.

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