The Tur (OC 207) explains that this berakha consists of three distinct parts, almost like three separate blessings:
First, we acknowledge that HaShem provides the needs of all souls, of everything He created. "Who creates many souls and [fills] their deficiency", that is, provides for their needs.
Second, we thank Him for everything He created in order to enliven us. This includes enjoyments which are not in the category of a need or lack, but rather are pleasures which enliven us. "For everything He created, in order to enliven all living things."
Finally, we acknowledge that HaShem is the "life of the worlds".
The first section, as we have translated it, seems straightforward. After we have eaten, we thank God for having provided for our needs and by extension for providing the needs of all His creatures. But Rebbe Natan of Breslav points out other more subtle connotations.
First of all, the wording of the phrase suggests that the main praise we are offering HaShem is that He has created "many souls". Without the additional word "and their deficiency", we would think that these "souls" refer to the food for which we are giving thanks!
Indeed, according to the Yerushalmi (Berakhot 6:1), the body of this blessing says merely: "Who creates many souls in order to enliven the soul of every living thing." Here it seems clear that the term "nefashot" or souls refers to the food we eat. According to the Yerushalmi's wording, the blessing explicitly refers to the hidden spirituality present in all permissible pleasures of this world; and even the customary wording implicitly hints at this spirituality and soulfulness.
Secondly, the plain sense of the wording suggests that we are thanking God for our deficiencies! We interpreted this as thanks for filling deficiency. Yet the concepts are related, for we get a sense of satisfaction from eating only because we feel hunger. And on the spiritual level, we are able to assimilate and absorb the "souls" of the permitted food only because they correspond to a particular spiritual hunger, which we have exactly because of our "deficiency" - which is just another way of saying a potential for growth.
The second part of the berakha continues in the same vein, referring to the ability of God's creation to enliven and invigorate us spiritually - to enliven the soul of all living things. Again, the emphasis is on the ability of material pleasures to provide spiritual sustenance. Rebbe Natan explains that this is why we give precedence in blessings to foods we like better: our personal likes and dislikes testify to our spiritual needs.
The closing of the blessing refers to HaShem as "the life of the worlds". In the mystic tradition, this particular appellation refers to that aspect of God's providence that provides an interface between the material and the spiritual worlds. (See for example Zohar Chayei Sarah I:132a.) It is through this interface that the material world is enlivened, for without spiritual force from on high the world would wither instantly.
Paradoxically, this interface also enlivens the upper, spiritual worlds! Their light is meant to illuminate the lower worlds; when the door is open to this illumination, this Divine light is stimulated and augmented. So this interface is indeed the life of the worlds - the spiritual and material worlds alike. This is an appropriate closing for a blessing that mentions the presence of God's spirit in the seemingly base elements of our material enjoyments.
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