The Dangers of Dieting

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The Dangers of Dieting

Avoid dietary setbacks to keep muscle and shed fat.

By Andrew Carruthers – Editor-In-Chief. Photos by Gary Phillips

Above: Steve Kuclo (Far Left), Cedric Mc Millan (Left Middle), Dexter Jackson (Right Middle) and William Bonac (Far Right) at the 2018 Arnold Classic Contest in Ohio, USA.

As bodybuilders, when it comes to dieting we tend to think in terms of losing body fat. But when that’s your only focus you may begin to overlook one of the most important and complex elements of the dieting process – your hormone levels. Hormones are crucial compounds that your body manufactures, and their levels can make or break your physique. Your body naturally produces all sorts of hormones to regulate bodily processes, support muscle repair, growth and recovery. When you diet to reduce body fat, your growth-supporting hormones may take a plunge, resulting in a loss of muscle. This article focuses on the biggest problems you can create by over-dieting: decreased thyroid functions, lower testosterone levels, immune-system compromise and lower leptin levels. But don’t worry, because we’ll also show you ways that you can approach your diet to avoid these setbacks and continue to keep the muscle, while still shedding the fat.

So what really happens when you over-diet?

Leptin levels decline – Leptin is an important hormone that helps your body regulate its weight. Over-dieting can cause a decline in leptin levels, which creates two dieting obstacles. Firstly, you may experience an increased intensity in food cravings (leading you to eat more than you should). Secondly, decreased leptin can also slow down your metabolic rate, making it more challenging to shed body fat. Both of these problems can have a severe impact on your ability to diet effectively.

Testosterone levels drop – When calories are cut too aggressively testosterone, the hormone that supports muscle growth declines, leading to a compromised ability to hang on to hard earned muscle mass. It’s crucial to keep testosterone levels up to hold on to muscle mass. It’s also important to keep testosterone levels elevated because doing so helps to cut body fat. Testosterone does this through two processes. It increases the number of beta-receptors (the part of a fat cell that helps to break down stored fat) and it inhibits the activity of lipoprotein lipase, an enzyme that “sucks” fat from your bloodstream and stores it near fat cells. The last thing you want as a dieter is a decline in your testosterone levels.

Impaired immunity – The immune system is your body’s built-in security guard, protecting it from germs, bacteria, viruses and anything else that might attack your body. Over-dieting, which decreases calories too much or for too long may ultimately have a negative effect on your immune system. A weak immune system has a direct impact on your body’s ability to hold muscle. Impaired immune function can also cause increases in cortisol, a stress hormone that destroys muscle. Elevated cortisol also tends to decrease testosterone. A body with a weak immune system finds it harder to destroy free radicals, the tiny components usually associated with stress, including the stress from weight training. Increased amounts of free radicals can lead to insulin resistance, a condition that elevates insulin levels, which is a contributor to the storage of body fat.

Thyroid function decreases – Specifically, thyroid hormone helps regulate how many calories your body burns each day. It also impacts muscle growth by speeding up or slowing down protein synthesis. Overly strict dieting can backfire because it may cause thyroid hormones levels to fall. The result is that your body burns fewer calories. Even though you’re eating less, you may not burn fat as effectively as when you were eating more calories. This reduction in your metabolic rate can negatively impact your body’s ability to lose body fat.

How can I combat these setbacks?

Don’t cut out simple carbs – In their quest to get shredded, many bodybuilders choose only slow-burning carbs, such as oats, beans, sweet and red potatoes. They reason that these carbs release less insulin than others and that lower insulin levels encourage fat burning. Although that’s true, we always suggest that for two out of every 10 training days, carbs should be fast burning. For example, a bodybuilder who has cut carbs to 350g per day stays at that number but switches to fast-digesting carbs, such as white rice mixed with raisins, bagels with jam or rice cakes. This seems to help preserve muscle tissue, most likely by increasing insulin levels. When insulin levels rise above typical levels, without higher calorie intake, the result is greater muscle maintenance without the storage of body fat. In other words you get the benefits of the anabolic effect of insulin without the fat storing effect.

Don’t reduce carbs by more than 30% – if you normally eat 500 grams of carbs each day don’t drop the amount to below 350 a day. A 30% drop in carbs is more than enough of a decline to encourage fat loss. Jumping straight into extreme low-carb dieting can backfire, flattening your muscles and triggering one or more of the four pitfalls mentioned above. Longer, but less severe diets are a much more effective way to burn body fat while maintaining muscle mass.

Eat less carbs when you’re not training – What about rest days? Normally you should aspire to Muscle Evolution’s recommendation of at least 2.5g of protein per kilogram of lean muscle weight, or even a little more when dieting, but only if your carb intake is sufficient. After all, you need carbs to train and to help support thyroid levels. However, on rest days you should dramatically decrease your carbs. Consume about 100g on your days off from training, but increase your protein intake to 4g per kilogram of body weight on those days. Temporarily increasing protein while decreasing carbs can improve the ability of muscles to uptake glucose. When you return to a higher carb intake, say 350g, and the gold standard 2.5g or more of protein per kilogram of body weight, the carbs are more readily stored in muscles, keeping them in an anabolic state during your dieting phase. If carbs are being deposited in muscles then they’re not headed for storage in body fat.

Don’t do too much cardio – There’s no doubt that cardio is an effective part of a fat loss strategy. It burns calories and much of what it burns is body fat, the keyword being much – not all. Excess cardio can be even more destructive than over-dieting in reducing important hormones. In other words, if you go overboard trying to burn calories with cardio you may lower hormone levels that help burn fat and build muscle. The result is that you end up looking terrible. Excess cardio is a dead end and can cause a severe loss in muscle mass. I remain steadfast in my belief that four 45 minutes sessions a week is the max you should do if you hope to keep your thyroid and testosterone levels up and your immune system potent. This however is body type dependent and those who store more fat might require more cardio.

Control your cheats – Bodybuilders always ask if cheating (eating a lot more on one day a week) is helpful. The premise is that greater food consumption once a week will help keep your metabolism from dropping. Cheating, generally defined as doubling up on carb intake, is permissible and even helpful only after you have hit a wall in your weight loss or, more important, no longer appear to be hardening up. That point is not reached weekly, so cheating one day a week is out. In my opinion, metabolic slowdown usually occurs 10-17 days into a diet, depending on the person. At that point, increasing calories, specifically carbs, can help you keep leptin, thyroid and testosterone levels, as well as the immune system from crashing. That should help your body and not hinder your bodybuilding progress.


Dieting involves a cascade of metabolic processes and, as a bodybuilding, you want to encourage the processes that support body fat reduction, while discourage those that tend to reduce muscle mass. To do this, moderate dieting over a longer period of time is a better approach than severe dieting over a short period of time. As with all things in bodybuilding, the best way to achieve an extreme physique is through consistency and moderation.


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