Do cardiovascular exercise.
While many people focus on cardiovascular exercise while avoiding weight training, there are others who do the opposite. Among certain groups of people, there are many myths about how cardiovascular exercise is bad for you, detrimental to someone trying to increase or maintain muscle mass, etc. These arguments usually reference data from studies on endurance athletes. Doing cardiovascular exercise does not mean running an ultramarathon. In fact, cardiovascular exercise of pretty much any reasonable intensity or duration is of benefit. While it is more likely that lean mass will be sacrified than with weight training, there is still a preferential loss of fat over muscle with physical activity. Additionally, epidemiological studies indicate that cardiovascular exercise is inversely correlated with the development of visceral adipose tissue (VAT) independently of body fat level. VAT is associated with a higher incidence of health problems, as well as an unsightly midsection.
The question then becomes which type of cardiovascular exercise is ideal for fat burning. As covered above, it is obviously not long-term endurance exercise, because although this causes a significant increase in caloric expenditure, a large amount comes from lean mass. There is another piece of misleading advice that you will commonly hear in this respect. Many will say that low intensity cardio (walking or light jogging) is best for weight loss because this is the "fat burning range" – a greater proportion of the calories burned comes from fat as opposed to alternative fuel sources such as glycogen. This may appear reasonable at first, but it really ignores the bigger picture. It is important to look at both calories burned during and after exercise, as exercise at a high enough intensity will lead to a longer-lasting increase in metabolic rate after exercise. Second, utilization of glycogen as opposed to fat during exercise is not necessarily a bad thing, as restoring the glycogen will still require calories. Also, if you look at it from the perspective of burning the most calories possible in the shortest period of time, the higher intensity, the better.
The ideal type of cardio for fat loss is short, high-intensity workouts, and this is supported by clinical studies. This causes the most calories to be burned in a given period of time and causes a greater increase in metabolic rate for a longer period of time after exercise. Additionally, the longer a cardio session is (especially after one hour), the more likely it is that loss of lean mass will occur, especially on a low calorie diet. This isn't to say that longer lasting, lower intensity cardiovascular exercise is bad, just that it is not the optimal way to lose fat. It is still good for your health, if kept within reason – definitely not something to avoid.
Don't overtrain
Overtraining is a misunderstood phenomenon, and there are different types of overtraining. Overtraining is a syndrome that is most common in endurance athletes. When bodybuilders use the term overtraining, they often mean "exercising with a greater frequency/intensity/duration than is optimal for muscle growth." It may also refer to training too often for the CNS to recover enough. While on a diet, the risk of all of these forms of overtraining is much greater. The primary things we want to avoid are muscle loss and too much CNS fatigue. This can be accomplished in a few ways.
First, do not start a new exercise routine, especially a new weightlifting one (although under some circumstances, such as someone who hasn't been weight training and is starting a weight loss plan, this is unavoidable) – this primarily applies if the new routine involves a greater workload or new exercises. I even think it is a good idea in some cases to not try to increase weights at all once you have started dieting. However, these rules depend on training experience, how well the diet and supplementation is being planned, and individual response.
Second, take one day completely off from training (both lifting and cardio) a week. Some light cardio or recreational exercise is fine, but nothing that will tax your system. Keep in mind that high intensity cardio sessions will drain you of energy as well.
Third, don't drop your calories lower than you need to to lose weight consistently (1-2 lbs. a week), as this will increase the chances of overtraining and losing muscle.
Fourth, listen to and know your body. If strength is decreasing, exercise frequency may be too great. You are going to have to learn what is optimal for you mostly by trial and error, as there are no set in stone rules. Some may be able to easily break all the rules listed above, while others will have to take them even further. If strength is decreasing, resist the urge to lift weights with bad form just to be using the same weights; you will be better off lowering them. Likewise, if you just can't find the motivation to do your cardio or weight training session, you may be training too often, and a few days off may help. On the other hand this shouldn't be used as an excuse, you have to be honest with yourself.
It is important to know that, for most dieters not using steroids and/or other drugs, some muscle loss is likely on a diet no matter how hard you try to prevent it. Many, especially beginners, want to lose body fat and increase muscle mass at the same time. It is important for you to get this idea out of your head, because although the magazines make it look commonplace, it is not, especially among those who have not been blessed with exceptional genetics. This is always something that one may want to attempt, but it shouldn't even be considered an option until one has quite a bit of experience and knowledge, or is planning on spending a large sum of money on supplements and drugs.
3. Supplements
Get extra nutrients.
During a low calorie diet is when you are most vulnerable to nutrient depletion, especially if you do not eat a large enough variety of foods. For this reason, extra nutrients should be supplemented with. However, supplements should not be relied upon to achieve adequate nutritional intake. You should still eat a nutritionally adequate diet to the best of your ability.
I recommend a good multivitamin/multimineral, a B vitamin complex, extra vitamins C and E, and some calcium, magnesium, and possibly potassium. A low dose zinc supplement may also be a good idea. Premenopausal women should make sure that their multi contains iron. One of the more important nutrients to supplement with on a diet is calcium. First, extra calcium may be needed when you are on a high protein diet. Also, calcium helps with fat loss through multiple mechanisms. An all-in-one calcium, magnesium, and vitamin D supplement is a good idea.
If possible, use stimulants.
There are a set of substances commonly referred to as "thermogenics," but I prefer the term stimulants, as thermogenic is a pretty broad category. Specifically, the stimulants I am referring to include caffeine, ephedrine, yohimbine, synephrine, nicotine, and others. Although it is common, I do not think it is a good idea to exceed simultaneous use of two, and definitely not three stimulants, as the risk of drug interactions increases with each substance added. My recommendation is to use caffeine along with one of the others. In my opinion, this group of substances represents the best in weight loss supplements/OTC options. Although there are many other options, they are usually less potent, or have less clinical data backing them up.
Of course, safety and side effects are the primary concerns with these substances. There seem to be two groups of people, those that won't use the substances because they consider them extremely dangerous and those that use them recklessly. Within normal parameters, these substances are very safe. This is especially true if my recommendations above are followed – using caffeine along with one other, instead of taking five at once thinking that they will all independently cause fat loss. In reality, very complex interactions occur, and you could be radically increasing side effects and/or decreasing effectiveness. Another way to ensure that the substance is being used safely is to stay in a safe dosage range.
In terms of side effects, many people complain about the "jitters," anxiety, or discomfort. For this reason they search everywhere for alternatives. In many cases it may indeed be best for these individuals to avoid these substances. However, people who think the side effects are too severe are also commonly those who are looking for a free ride. As I covered above, if you want to lose weight, you are going to have to accept discomfort. If one wants to reach their goal badly enough, they shouldn't be too concerned with some uncomfortable side effects. There is a segment of the population that is quite sensitive to stimulants (with a greater percentage of them being women), and this cannot be discounted, but one should ponder whether they fall under this category or the category of people who just want everything to be easier than it really is. Another important consideration is that with regular use, side effects significantly diminish.
With that said, stimulant use is definitely not necessary for weight loss (see #4 in this section). Also, in the previously mentioned sensitive individuals, as well as those with health problems, and those who are taking prescription drugs with which these substances may interact negatively, stimulants should be avoided.