best friend will probably not tell you any of the wisdom that follows,
You need a lot more protein if you are on a low calorie (restricted calorie) diet; if you don't get it, you lose protein from vital organs and tissues, and this may be irreversible (Bistrian et al., 1981; Oi et al., 1987; Pasquali et al., 1987a; Vasquez et al., 1987; Gougeon-Reyburn et al., 1992a). Why ruin your body on a bad diet?
On diets with the same numbers of calories, weight loss is significantly greater when the calories don't come from carbohydrates (Rabast et al., 1979; Oi et al., 1987). It may be cheaper to eat carbohydrates, and it is certainly cheaper to make diet products that are low in protein, but don't expect to lose your weight too quickly! In fact, you may even plateau or start putting weight on again.
High protein diets preserve functional tissues and maintain your capacity for physical performance (Davis & Phinney, 1990). What's the use of a diet that leaves you listless in your armchair all day? The end result of a good diet should be a slimmer, more vital, you, not a wilting lily who can hardly summon the strength to get out of bed in the morning!
Diets can affect brain function adversely (Anderson et al., 1990). The changes that occur may be countered by increasing protein intake (Nathan & Rolland, 1987; Wurtman, 1987). Again, the end result of a good diet should be a slim and lively person, with a personality to match, enjoying their new life. Definitely NOT a morose and sullen wraith, reaching for the Prozac half a dozen times a day!
Protein has a thermogenic effect that helps offset the decline in metabolic rate which occurs on most low calorie diets (Garrow, 1978). Why tolerate lack of energy and plateauing if you don't have to? Exercise is beneficial because it also has a thermogenic effect, but don't expect too much from it in terms of weight loss (Garrow, 1978; Poehlmann et al., 1991)! However, the exercise is a very valuable aid to becoming fit again, and in fact, fitter than you ever were before.
Don't think that low means no!
§ Sodium is an essential nutrient; you need a minimum of 2300 mg per day (5 - 6 grams of salt; about 1 teaspoon) on any weight loss diet (Gougeon-Reyburn et al., 1991b). Dieters have died because they didn't get enough sodium! Don't join this club! Those who are not on a diet can get by with less salt, but they still need some.
§ Fat is essential, both in your normal diet and in weight loss diets. Diets totally without fat kill people in 2 - 4 weeks (Goodwin, & Wilmore, 1988); diets which don't have enough essential fatty acids just cause side effects that may be merely annoying, such as thinning of hair or skin problems, or expensive, such as gallstones (FAO/WHO, 1980; Siguel & Schaefer, 1988; Jones, 1990).
For a normal diet, the advice that 25% - 30% of the calories should come from good "mixed" fat (approximately equal amounts of saturated, mono-unsaturated and poly-unsaturated fats) is excellent, provided that the trans fatty acids are avoided. This is difficult to apply to low calorie diets, since the absolute requirement for the essential fatty acids (the EFAs) may actually go up on low calorie diets, but low calorie diets can be supplemented by special essential fatty acid capsules, containing the omega-6 and omega-3 essential fatty acids with the long names (Jones, 1990). As EFAs, these pack a lot of punch (they are much more potent than the EFAs found in normal oils), so you don't have to take in hundreds of calories to meet your EFA requirements. If you want to get technical so early in the book, these EFAs are gamma-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid, which we abbreviate as GLA, EPA and DHA respectively.
A recent opinion poll showed that 17% of the American public thought that the healthiest diet was zero-fat. It is fortunate that achieving a zero-fat diet is almost impossible for the average person, since the funeral homes would not be able to cope!
An investigation of many popular American diet programs showed that just about all were deficient in essential fatty acids. A few diet programs include obligatory essential fatty acid supplementation, and in most countries other than the USA, Government legislation makes inclusion of essential fatty acids in diet products compulsory!
Talking about fat, the trans fatty acids (present in hydrogenated or partially hydrogenated domestic oils) are much more harmful to your health than saturated fats, and many countries have adopted legislation to reduce or eliminate them in foods. You need not worry about small amounts; provided that you have an adequate essential fatty acid intake, your body will cope. The official point of view depends on where you live; in England, no more than 5 grams per day (a teaspoon of margarine or vegetable shortening), but in Holland and Denmark, they have to be out completely by the year 2000. In the United States, there is no official point of view, and trans fatty acids may even be labelled as mono- and polyunsaturated fats on labels! The poor public really needs to know some oil and fat chemistry to work out whether a product is safe or not!
It would, indeed, be difficult to avoid the trans fatty acids completely, since small amounts of partially hydrogenated vegetable oils are used in most prepared foods, but shun things like margarines and chocolate-type coatings made with hydrogenated domestic oils. Outside the United States, margarines made without hydrogenation from native vegetable oils are available, and they are nutritionally superb.
The good diet program is based on sound nutritional principles, ensures that your diet does not harm you through protein loss and deficiencies, makes you feel as well as possible, and is supervised by staff who care more about you and your wellbeing than they do about your pocket-book!
The bad diet program will do nothing for you except impair your health and deplete your bank account!
To summarize the points of a good and safe diet, intended to help you lose weight:
Diet programs which do not meet all these requirements simultaneously are potentially hazardous; they may cause adverse effects, and may result in irreparable harm in either the short or the long term.
diets which are high in protein, appropriately supplemented with vitamins,
minerals and essential fatty acids, have proven the safest and most
effective types of diet in weight loss.