Biology’s Response to Dieting – Review

If one understands the basics of human biology and its adaptive mechanisms, sustained weight loss can be achieved. I have recently stumbled upon a truly superb article. I feel I have no choice but to review it. The information in this study will truly help everybody in their fitness journey. The referenced article is a review of several studies that point to the metabolic adaptations the body undergoes while “dieting.”

Biology’s Response to Dieting

“…in contrast to its subtle, permissive role in the development of obesity, biology has a more prominent, causal role in weight regain after energy-restricted weight loss. Countering this metabolic drive to regain lost weight may be the most significant challenge for obesity therapeutics in the coming decades.” (MacLean et al)

I had a professor who had two fundamental rules about life:
1. People seek and desire simplicity
2. Nothing is simple

The latter is especially true concerning the human body and its adaptations. There is never only one cause for one effect. This is especially true in regards to body weight.

Three Key Factors:
1. Biological
2. Environmental
3. Behavioral Pressures

*It should go without saying that genetics influence each of the above stated factors; however, I will not assume.

Before diving in too much further, let’s breakdown how one gains weight. Simply put (but please keep in mind the two fundamental rules), if one consumes more calories than that said person burns off, weight gain is likely. It is very easy to see how a high caloric intake coupled with low physical activity level would produce weight gain. Again, that is weight gain, in an ever so small, nutshell (i.e. pistachio).

Set-Point

As you probably know, the body is always trying to maintain balance (homeostasis). Either one of the 3 factors can tilt this balance to either weight loss or weight gain, depending on how they’re manipulated. The biological factor is primarily responsible for this balance. It will do its best to keep you from losing too much weight (survival) as well as keep you from gaining too much weight.

The above balance can also be called the “set-point.” Basically, this is the point your body basis everything off of. If your caloric intake is higher than what your body’s set-point is, you’ll gain weight and vise versa. This set-point is vitally important to any desire to change body composition.

The above biological balance response is intertwined with environmental and behavioral factors. The environment many American’s find themselves in is much in favor of weight gain. The countless options of high fat, high carb, and low protein are all but guaranteeing a positive caloric balance.

Consequences of Nutritional Choices

The body’s desire for homeostasis adjusts to these environmental and behavioral factors. One of these adjustments comes in the form of a new set-point. This new set-point is at a higher body weight with the aforementioned high fat, high carb, low protein diet. This scenario would be considered diet-induced obesity (DIO). The other side of the coin is called obesity-resistant (OR). Those who are blessed with this homeostasis adaptation will have a positive energy balance at first just like the DIO group. However, their body will catch on to this and increase fat oxidation, increase energy expenditure (EE), and reestablish energy balance. However, the OR typically don’t struggle with weight gain or failed attempts to diet so they will not be discussed any further.

It should be noted that if the caloric increase is too high, it may be too difficult for the body to establish a new set-point. Therefore, weight gain would steadily increase. The same cannot be said for weight loss however. If you’re losing weight on 1,000 calories, it doesn’t mean you’ll lose more on 500 or 0 calories. The body will eventually adapt to such a caloric deficit, as one cannot consume negative calories. The eventual adaptations to 0 calories would be death and is not advised.

Once again, and I can’t stress enough, this is not going to be true for all individuals. As stated before, nothing is simple and individual genetics play a significant role. 

Note: One should diet on as many calories as possible to maintain sanity and prevent an extreme drop in metabolic rate.

There is a beautifully illustrated graph on the article. I highly recommend you go check it out.

The Culprit 

Your body will adapt and create a new set-point to the lower calorie weight loss diet. When this happens, weight loss either slowly creeps or comes to a screeching halt. Your body has adapted to a lower caloric intake and can sustain its weight. This is considered by many to be a weight-loss plateau. To continue weight loss, you must dip below this new set-point.

To maintain this new body weight, the weight loss strategy implemented must be maintained. After the diet is over, many people immediately go back to whatever they were eating before. This can explain why people regain the weight they’ve previously lost almost immediately post-diet. The difference now is that the set-point is much lower. In most cases, this individual can expect to regain the weight they’ve just lost plus some.

Hormonal Adaptations: Leptin & Insulin

The chronic use of a low calorie diet can greatly effect hormones. The two I’ll discuss here are leptin and insulin. These hormones are good determinants of the basic state of the body (catabolic or anabolic) when the body is in an imbalance. Without getting too in-depth, lower leptin levels mean a decrease in fat utilization for fuel. For those curious, this is the basis for “re-feeds” or cheat meals. This brief increase in caloric consumption is believed to increase leptin levels back to normal. Theoretically, this restores your body’s ability to burn fat.

Insulin levels are a little more difficult to determine as one can increase insulin resistance through a variety of mechanisms. In most cases, you would want to be somewhat insulin resistant. Insulin is a storage hormone. Therefore, the higher the insulin levels the more anabolic the body is in most instances. That applies to muscle gain as well as fat gain. The latter is often left out of anabolism, but it’s important not to forget! Lower calorie diets will decrease insulin levels. Exercise will lower insulin levels and is recommended over lower calorie diets.

Appetite Control

Any successful diet must prevent an increase in appetite. Lower calorie diets can greatly increase appetite. As previously stated, it is important to lose weight on a diet that has as many calories as possible. However, one must remain in a negative caloric balance in order to promote weight loss. Appetite is more of a psychological factor but is vitally important. Most diets fail due to lack of adherence (ability to stick to it). The diet that works is the one that you can stick to and maintain LONG TERM. There are no quick fixes to long term solutions.

It should come to no surprise that those who actively seek out weight loss demonstrate a more controlled habit of eating. Obviously, the more motivated you are at attaining your goal the less psychological factors will effect you. People with less constraint about food are more likely to be less motivated and less successful. Again, this should come at no surprise.

The mind is a powerful tool; use it to your benefit, not detriment.

“…satisfactory amounts of weight loss usually do not occur without intentionally restricting energy intake” (MacLean et al).

Metabolic Flexibility

This metabolic adaptation allows the body to adjust fuel preferences (glucose, free fatty acids, ketones, etc)  according to metabolic challenges that stress the body. These stressors can come from fasting (my personal favorite), exercise, eating, etc. Metabolic inflexibility is common among obese individuals. After extended periods of under-eating, the body responds to the incoming food differently. The brain can continue to send signals to alert the body of malnutrition.

This will tell the body to store necessary nutrients for later use. All too often this homeostasis mechanism is referred to as “survival mode.” These biological adaptations may be similar to what you might find when one is truly in survival mode, but this is merely speculation. In the context I am speaking, your body is far from “survival mode.” This is only an adaptation to a caloric intake below your current set-point.

If you think about it, every single adaptation the body makes could be argued as a “survival mechanism.” Simple put, one is not on the brink of death after a single skipped meal.

I don’t want to get off task and this blog post is already lengthy so for any rebuttals about the “survival mode” theory, please consult my previous blog post, “Shining a Light – Debunking of Some Common Fitness Myths” and/or check this study out.

Adipose Tissue Adaptations

Perhaps, the adaptations of fat tissue (adipose) is the one to demonize. The term fat loss is somewhat incorrect. You do lose fat; however, you do not lose fat cells. When you lose fat, the fat cells shrink. They do not disappear. However, the smaller size of these fat cells are much more sensitive to the anti-fat burning effects of insulin. These cells favor energy (fat) storage compared to normal sized fat cells.

It is important to note that the smaller fat cells still have the ability to store the same amount of fat as they would at normal size. Energy-restricted weight loss programs pave the way for these fat cells to quickly fill back up once overfeeding occurs. This is a contributing factor to post-diet weight regain in lean and obese individuals.

I’m afraid it could potentially get worse, much worse. Once all of your given fat cells are full, your body begins to create more. This is something you want to avoid at all costs. As I previously stated, fat cells do not go away, they merely shrink. To say that fat cells can never be destroyed may not be entirely correct. So, for the time being, we’re going to say that it’s extremely difficult to get rid of them. Regardless, this is a situation you want to avoid.

The more fat cells you have, the harder it’s going to be to lose unwanted fat. Furthermore,  the more fat cells you have the easier it’s going to be to regain body fat. That’s just part of the beast.

Solution

Now that I have completely destroyed all hope you have of getting lean, let me provide you a potential solution.

“To be successful in the long term, our strategies for preventing weight regain may need to be just as comprehensive, persistent, and redundant, as the biological adaptations they are attempting to counter.” (MacLean et al)

We can implement different strategies to use these biological adaptations to our advantage. Below I have given you a few things to consider.

1. High Protein, Low Carbohydrate, Moderate Fat Diet

I’m sure this comes to no surprise to most of you. I myself live on a high protein, low carb, moderate fat approach and have been known to suggest it from time to time. Let me be clear:

Yes, I realize that my caloric intake is around 2,100 kcal. The reason: I have fell victim to these metabolic adaptations I’ve previously discussed. I did three bodybuilding shows and it spanned out from early February until the beginning of August. After my last show, I immediately began to eat whatever I wanted and in whatever quantity I so desired. I am currently in the process of restoring my metabolism back to where it was before I started dieting. (Even knowledgeable professionals make mistakes).

My fat intake is a little lower than my recommended 0.4 – 0.6g. It has been much, much higher in the past, but I have found this level to be a bit better for my current situation and goals. (This is as of now, don’t expect this to be permanent as it will be forever fluctuating, I’m afraid.)

I do not fall victim to the symptoms of low carb diets. My energy is great, if not better. I train fasted 95% of the time so they wouldn’t enhance my workouts anyway. For a more extensive review on carbs, please stay tuned. There will be a whole, seperate post on nothing but that three-element macronutrient soon.

The brief rationale for a high protein intake is as follows:
A. Better effect on satiety
B. More metabolically expensive to digest (compared to carbs and fats)
C. Protein is important to muscle preservation while dieting
D. Excess protein is least likely to be stored as fat (compared to carbs and fats)

2. Strategic “Cheats” or “Re-Feeds”

A. Keep fat intake to a minimum

B. No more frequently than 1 x week

The general rule of thumb here is no more than 1 x week. Leaner individuals and experienced trainees may require a re-feed more frequently than those who are not as lean or as experienced in regard to training. However, I feel like 1 x week is the most frequent and beneficial. However, as usual, this must be determined on a case by case basis.

In my opinion, “cheats” are not required if adequate carbohydrates are consumed and muscle glycogen stores remain full.

3. Finding Set-Point

First and foremost, you must know your set-point. This isn’t too difficult to find; it just takes a little patience. I’m assuming everyone is tracking their calories. If you are not, you’re gonna need to start in order to find your set-point.

Keep your calories as consistent as possible for a week. For example, my calories this week are 2,100. I want to consume no more and no less than 2,100. However, hitting the exact number may be difficult. I will allow myself a 50 kcal window in each direction: 2,050-2,150 kcal.

You will also want to track body weight. Weigh yourself each morning, immediately after waking and going to bathroom. Keep the times as consistent as possible. You want to control all variables. At the end of the week you are going to average body weight and caloric intake. This is week 1.

You will do the same thing the following week with ONE adjustment: increase calories by 100. For me, this increase will come from carbohydrates as protein intake is already high. You may have to work up to the higher amounts of protein. That will be user-dependant. The main focus is an increase in caloric intake by 100 kcal.

You will continue to do this week after week until you notice a significant increase in body weight. Significant is 3-5lb increase based on the weekly average. Once you have found this, go back to last caloric number in which you maintained body weight. This will be your set-point.

Like I said, finding your set-point requires some patience and persistence. But, once you’ve found it, you’re half way there. You want to strive to lose 1-2lbs/week. We will decrease our set-point calories by 500/day. Cut these calories from carbs and fats primarily. Don’t allow this deficit to take you below 1,200 kcal/day. If that’s the case, remain at 1,200 kcal and get the extra calorie burn from physical activity.

I recommend you couple any diet with an exercise routine. The results will be much better, but I will not get into exercise prescription in this post.

Conclusion

There are several biological functions that effect your body’s ability to maintain weight loss. Immediately returning back to ‘normal’ eating post-diet can result in weight regain. One must diet down slowly and reverse diet equally as slow to allow the body’s set-point to re-establish at a higher caloric load.

Maclean, Paul S., Audrey Bergouignan, Marc-Andre Cornier, & Matthew R. Jackman. “Body’s response to dieting: the impetus for weight regain.” AJP-Regul Integr Comp Physiol. Vol 301. Web. 2011.

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